For more information on Character Encoding on the web, see Alan
Flavell's excellent HTML Character
Set Issues reference.
This error can also be triggered by formatting characters embedded in
documents by some word processors. If you use a word processor to edit
your HTML documents, be sure to use the "Save as ASCII" or similar
command to save the document without formatting information.
141: ID X already defined
An "id" is a unique identifier. Each time this attribute is used in a document
it must have a different value. If you are using this attribute as a hook for
style sheets it may be more appropriate to use classes (which group elements)
than id (which are used to identify exactly one element).
183: reference to non-existent ID X
This error can be triggered by:
A non-existent input, select or textarea element
A missing id attribute
A typographical error in the id attribute
Try to check the spelling and case of the id you are referring to.
187: no docum will parse without validation
The document type could not be determined, because the document had no correct DOCTYPE declaration. The document does not look like HTML, therefore automatic fallback could not be performed, and the document was only checked against basic markup syntax.
from our FAQ, or use the validator's
Document Type option to validate your document against a specific Document Type.
246: unclosed start-tag requires SHORTTAG YES
The construct &foo&bar& is valid in HTML (it is an example of the rather obscure “Shorttags” feature)
In most cases, this is a typo that you will want to fix. If you really want to use shorttags,
be aware that they are not well implemented by browsers.
247: NET-enabling start-tag requires SHORTTAG YES
For the current document, the validator interprets strings like
&FOO /& according to legacy rules that
break the expectations of most authors and thus cause confusing warnings
and error messages from the validator. This interpretation is triggered
by HTML 4 documents or other SGML-based HTML documents. To avoid the
messages, simply remove the "/" character in such contexts. NB: If you
expect &FOO /& to be interpreted as an
XML-compatible "self-closing" tag, then you need to use XHTML or HTML5.
This warning and related errors may also be caused by an unquoted
attribute value containing one or more "/". Example:
&a href=http://w3c.org&W3C&/a&.
In such cases, the solution is to put quotation marks around the value.
248: unclosed end-tag requires SHORTTAG YES
The construct &/foo&bar& is valid in HTML (it is an example of the rather obscure “Shorttags” feature)
In most cases, this is a typo that you will want to fix. If you really want to use shorttags,
be aware that they are not well implemented by browsers.
323: DTD did not contain element declaration for document type name
A DOCTYPE declares the version of the language used, as well as what the root
(top) element of your document will be. For example, if the top element
of your document is &html&, the DOCTYPE declaration
will look like: "&!DOCTYPE html".
In most cases, it is safer not to type or edit the DOCTYPE declaration at all,
and preferable to let a tool include it, or copy and paste it from a
325: reference to entity X for which no system identifier could be generated
This is usually a cascading error caused by a an undefined entity
reference or use of an unencoded ampersand (&) in an URL or body
text. See the previous message for further details.
333: empty start-tag
The construct && is sometimes valid in HTML (it is an example of the rather obscure “Shorttags” feature)
In most cases, this is a typo that you will want to fix. If you really want to use shorttags,
be aware that they are not well implemented by browsers.
334: empty end-tag
The construct &/& is valid in HTML (it is an example of the rather obscure “Shorttags” feature)
In most cases, this is a typo that you will want to fix. If you really want to use shorttags,
be aware that they are not well implemented by browsers.
338: cannot generate system identifier for general entity X
An entity reference was found in the document, but there is no reference
by that name defined. Often this is caused by misspelling the reference
name, unencoded ampersands, or by leaving off the trailing semicolon (;).
The most common cause of this error is unencoded ampersands in
URLs as described by the WDG in "Ampersands
Entity references start with an ampersand (&) and end with a
semicolon (;). If you want to use a literal ampersand in your document
you must encode it as "&" (even inside URLs!). Be
careful to end entity references with a semicolon or your entity
reference may get interpreted in connection with the following text.
Also keep in mind that named entity references are case-
&A and & are different characters.
If this error appears in some markup generated by PHP's session handling
explanations and solutions to your problem.
Note that in most documents, errors related to entity references will
trigger up to 5 separate messages from the Validator. Usually these
will all disappear when the original problem is fixed.
344: no docum implying X
The checked page did not contain a document type ("DOCTYPE") declaration.
The Validator has tried to validate with a fallback DTD,
but this is quite likely to be incorrect and will generate a large number
of incorrect error messages. It is highly recommended that you insert the
proper DOCTYPE declaration in your document -- instructions for doing this
are given above -- and it is necessary to have this declaration before the
page can be declared to be valid.
378: no system id specified
Your document includes a DOCTYPE declaration with a public identifier
(e.g. "-//W3C//DTD XHTML 1.0 Strict//EN") but no system identifier
(e.g. "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"). This is
authorized in HTML (based on SGML), but not in XML-based languages.
If you are using a standard XHTML document type, it is recommended to use exactly
one of the DOCTYPE declarations from the
387: S separator in comment declaration
This may happen if you have consecutive comments but did not close one of them properly.
The proper syntax for comments is &!-- my comment --&.
394: reference not terminated by REFC delimiter
If you meant to include an entity that starts with "&", then you should
terminate it with ";".
Another reason for this error message is that
you inadvertently created an entity by failing to escape an "&"
character just before this text.
403: reference to external entity in attribute value
This is generally the sign of an ampersand that was not properly escaped for inclusion
in an attribute, in a href for example. You will need to escape all instances of '&'
404: character X is the first character of a delimiter but occurred as data
This message may appear in several cases:
You tried to include the "&" character in your page: you should escape it as "&"
You used an unescaped ampersand "&": this may be valid in some contexts,
but it is recommended to use "&", which is always safe.
Another possibility is that you forgot to close quotes in a previous tag.
407: NET-enabling start-tag not immediately followed by null end-tag
This error may occur when there is a mistake in how a self-closing tag is closed, e.g '.../ &'.
The proper syntax is '... /&' (note the position of the space).
410: reference to non-SGML character
You've included a character reference to a character that is not defined
in the document type you've chosen. This is most commonly caused by
numerical references to characters from vendor proprietary
character repertoires. Often the culprit will be fancy or typographical
quote marks from either the Windows or Macintosh character repertoires.
The solution is to reference UNICODE characters instead. A list of
common characters from the Windows character repertoire and their
UNICODE equivalents can be found in the document "On the use of some MS Windows characters in HTML" maintained by
Errors without explanation
The following validation errors do not have an explanation yet. We invite you to use the
to send your suggestions.
0: length of name must not exceed NAMELEN (X)
1: length of parameter entity name must not exceed NAMELEN less the length of the PERO delimiter (X)
2: length of number must not exceed NAMELEN (X)
3: length of attribute value must not exceed LITLEN less NORMSEP (X)
4: a name group is not allowed in a parameter entity reference in the prolog
5: an entity end in a token separator must terminate an entity referenced in the same group
6: character X invalid: only Y and token separators allowed
7: a parameter separator is required after a number that is followed by a name start character
8: character X invalid: only Y and parameter separators allowed
9: an entity end in a parameter separator must terminate an entity referenced in the same declaration
10: an entity end is not allowed in a token separator that does not follow a token
11: X is not a valid token here
12: a parameter entity reference can only occur in a group where a token could occur
13: token X has already occurred in this group
14: the number of tokens in a group must not exceed GRPCNT (X)
15: an entity end in a literal must terminate an entity referenced in the same literal
16: character X invalid: only minimum data characters allowed
18: a parameter literal in a data tag pattern must not contain a numeric character reference to a non-SGML character
19: a parameter literal in a data tag pattern must not contain a numeric character reference to a function character
20: a name group is not allowed in a general entity reference in a start tag
21: a name group is not allowed in a general entity reference in the prolog
22: X is not a function name
23: X is not a character number in the document character set
24: parameter entity X not defined
26: RNI delimiter must be followed by name start character
29: comment started here
30: only one type of connector should be used in a single group
31: X is not a reserved name
32: X is not allowed as a reserved name here
33: length of interpreted minimum literal must not exceed reference LITLEN (X)
34: length of tokenized attribute value must not exceed LITLEN less NORMSEP (X)
35: length of system identifier must not exceed LITLEN (X)
36: length of interpreted parameter literal must not exceed LITLEN (X)
37: length of interpreted parameter literal in data tag pattern must not exceed DTEMPLEN (X)
39: X invalid: only Y and parameter separators are allowed
40: X invalid: only Y and token separators are allowed
41: X invalid: only Y and token separators are allowed
43: X declaration not allowed in DTD subset
44: character X not allowed in declaration subset
45: end of document in DTD subset
46: character X not allowed in prolog
48: X declaration not allowed in prolog
49: X used both a rank stem and generic identifier
50: omitted tag minimization parameter can be omitted only if OMITTAG NO is specified
51: element type X already defined
52: entity reference with no applicable DTD
53: invalid comment declaration: found X outside comment but inside comment declaration
54: comment declaration started here
55: X declaration not allowed in instance
56: non-SGML character not allowed in content
57: no current rank for rank stem X
58: duplicate attribute definition list for notation X
59: duplicate attribute definition list for element X
60: entity end not allowed in end tag
61: character X not allowed in end tag
62: X invalid: only S separators and TAGC allowed here
66: document type does not allow element X assuming missing Y start-tag
67: no start tag specified for implied empty element X
72: start tag omitted for element X with declared content
74: start tag for X omitted, but its declaration does not permit this
75: number of open elements exceeds TAGLVL (X)
77: empty end tag but no open elements
78: X not finished but containing element ended
80: internal parameter entity X cannot be CDATA or SDATA
81: character X not allowed in attribute specification list
83: entity end not allowed in attribute specification list except in attribute value literal
84: external parameter entity X cannot be CDATA, SDATA, NDATA or SUBDOC
85: duplicate declaration of entity X
86: duplicate declaration of parameter entity X
87: a reference to a PI entity is allowed only in a context where a processing instruction could occur
88: a reference to a CDATA or SDATA entity is allowed only in a context where a data character could occur
89: a reference to a subdocument entity or external data entity is allowed only in a context where a data character could occur
90: a reference to a subdocument entity or external data entity is not allowed in replaceable character data
91: the number of open entities cannot exceed ENTLVL (X)
92: a reference to a PI entity is not allowed in replaceable character data
93: entity X is already open
94: short reference map X not defined
95: short reference map in DTD must specify associated element type
96: short reference map in document instance cannot specify associated element type
97: short reference map X for element Y not defined in DTD
98: X is not a short reference delimiter
99: short reference delimiter X already mapped in this declaration
100: no document element
102: entity end not allowed in processing instruction
103: length of processing instruction must not exceed PILEN (X)
104: missing PIC delimiter
106: X is not a member of a group specified for any attribute
109: an attribute value specification must start with a literal or a name character
110: length of name token must not exceed NAMELEN (X)
113: duplicate definition of attribute X
114: data attribute specification must be omitted if attribute specification list is empty
115: marked section end not in marked section declaration
116: number of open marked sections must not exceed TAGLVL (X)
117: missing marked section end
118: marked section started here
119: entity end in character data, replaceable character data or ignored marked section
126: non-impliable attribute X not specified but OMITTAG NO and SHORTTAG NO
128: first occurrence of CURRENT attribute X not specified
129: X is not a notation name
130: X is not a general entity name
132: X is not a data or subdocument entity
133: content model is ambiguous: when no tokens have been matched, both the Y and Z occurrences of X are possible
134: content model is ambiguous: when the current token is the Y occurrence of X, both the a and b occurrences of Z are possible
135: content model is ambiguous: when the current token is the Y occurrence of X and the innermost containing AND group has been matched, both the a and b occurrences of Z are possible
136: content model is ambiguous: when the current token is the Y occurrence of X and the innermost Z containing AND groups have been matched, both the b and c occurrences of a are possible
138: comment declaration started here
140: data or replaceable character data in declaration subset
142: ID X first defined here
143: value of fixed attribute X not equal to default
144: character X is not significant in the reference concrete syntax and so cannot occur in a comment in the SGML declaration
145: minimum data of first minimum literal in SGML declaration must be ""ISO "" or ""ISO
(ENR)"" or ""ISO
(WWW)"" not X
146: parameter before LCNMSTRT must be NAMING not X
147: unexpected entity end in SGML declaration: only X, S separators and comments allowed
148: X invalid: only Y and parameter separators allowed
149: magnitude of X too big
150: character X is not significant in the reference concrete syntax and so cannot occur in a literal in the SGML declaration except as the replacement of a character reference
151: X is not a valid syntax reference character number
152: a parameter entity reference cannot occur in an SGML declaration
153: X invalid: only Y and parameter separators are allowed
154: cannot continue because of previous errors
155: SGML declaration cannot be parsed because the character set does not contain characters having the following numbers in ISO 646: X
156: the specified character set is invalid because it does not contain the minimum data characters having the following numbers in ISO 646: X
157: character numbers declared more than once: X
158: character numbers should have been declared UNUSED: X
159: character numbers missing in base set: X
160: characters in the document character set with numbers exceeding X not supported
161: invalid formal public identifier X: missing //
162: invalid formal public identifier X: no SPACE after public text class
163: invalid formal public identifier X: invalid public text class
164: invalid formal public identifier X: public text language must be a name containing only upper case letters
165: invalid formal public identifer X: public text display version not permitted with this text class
166: invalid formal public identifier X: extra field
167: public text class of public identifier in notation identifier must be NOTATION
168: base character set X is unknown
169: delimiter set is ambiguous: X and Y can be recognized in the same mode
170: characters with the following numbers in the syntax reference character set are significant in the concrete syntax but are not in the document character set: X
171: there is no unique character in the document character set corresponding to character number X in the syntax reference character set
172: there is no unique character in the internal character set corresponding to character number X in the syntax reference character set
173: the character with number X in ISO 646 is significant but has no representation in the syntax reference character set
174: capacity set X is unknown
175: capacity X already specified
176: value of capacity X exceeds value of TOTALCAP
177: syntax X is unknown
178: UCNMSTRT must have the same number of characters as LCNMSTRT
179: UCNMCHAR must have the same number of characters as LCNMCHAR
180: number of open subdocuments exceeds quantity specified for SUBDOC parameter in SGML declaration (X)
181: entity X declared SUBDOC, but SUBDOC NO specified in SGML declaration
182: a parameter entity referenced in a parameter separator must end in the same declaration
184: generic identifier X used in DTD but not defined
185: X not finished but document ended
186: cannot continue with subdocument because of previous errors
188: no internal or external document typ will parse without validation
189: this is not an SGML document
190: length of start-tag before interpretation of literals must not exceed TAGLEN (X)
191: a parameter entity referenced in a token separator must end in the same group
192: the following character numbers are shunned characters that are not significant and so should have been declared UNUSED: X
193: there is no unique character in the specified document character set corresponding to character number X in ISO 646
194: length of attribute value must not exceed LITLEN less NORMSEP (-X)
195: length of tokenized attribute value must not exceed LITLEN less NORMSEP (-X)
196: concrete syntax scope is INSTANCE but value of X quantity is less than value in reference quantity set
197: public text class of formal public identifier of base character set must be CHARSET
198: public text class of formal public identifier of capacity set must be CAPACITY
199: public text class of formal public identifier of concrete syntax must be SYNTAX
200: when there is an MSOCHAR there must also be an MSICHAR
201: character number X in the syntax reference character set was specified as a character to be switched but is not a markup character
202: character number X was specified as a character to be switched but is not in the syntax reference character set
203: character numbers X in the document character set have been assigned the same meaning, but this is the meaning of a significant character
204: character number X assigned to more than one function
205: X is already a function name
206: characters with the following numbers in ISO 646 are significant in the concrete syntax but are not in the document character set: X
207: general delimiter X consists solely of function characters
208: letters assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT: X
209: digits assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT: X
210: character number X cannot be assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT because it is RE
211: character number X cannot be assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT because it is RS
212: character number X cannot be assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT because it is SPACE
213: separator characters assigned to LCNMCHAR, UCNMCHAR, LCNMSTRT or UCNMSTRT: X
214: character number X cannot be switched because it is a Digit, LC Letter or UC Letter
215: pointless for number of characters to be 0
216: X cannot be the replacement for a reference reserved name because it is another reference reserved name
217: X cannot be the replacement for a reference reserved name because it is the replacement of another reference reserved name
218: replacement for reserved name X already specified
219: X is not a valid name in the declared concrete syntax
220: X is not a valid short reference delimiter because it has more than one B sequence
221: X is not a valid short reference delimiter because it is adjacent to a character that can occur in a blank sequence
222: length of delimiter X exceeds NAMELEN (Y)
223: length of reserved name X exceeds NAMELEN (Y)
224: character numbers assigned to both LCNMCHAR or UCNMCHAR and LCNMSTRT or UCNMSTRT: X
225: when the concrete syntax scope is INSTANCE the syntax reference character set of the declared syntax must be the same as that of the reference concrete syntax
226: end-tag minimization should be O for element with declared content of EMPTY
227: end-tag minimization should be O for element X because it has CONREF attribute
228: element X has a declared content of EMPTY and a CONREF attribute
229: element X has a declared content of EMPTY and a NOTATION attribute
230: declared value of data attribute cannot be ENTITY, ENTITIES, ID, IDREF, IDREFS or NOTATION
231: default value of data attribute cannot be CONREF or CURRENT
232: number of attribute names and name tokens (X) exceeds ATTCNT (Y)
233: if the declared value is ID the default value must be IMPLIED or REQUIRED
234: the attribute definition list already declared attribute X as the ID attribute
235: the attribute definition list already declared attribute X as the NOTATION attribute
236: token X occurs more than once in attribute definition list
237: no attributes defined for notation X
238: notation X for entity Y undefined
239: entity X undefined in short reference map Y
240: notation X is undefined but had attribute definition
241: length of interpreted parameter literal in bracketed text plus the length of the bracketing delimiters must not exceed LITLEN (X)
242: length of rank stem plus length of rank suffix must not exceed NAMELEN (X)
243: document instance must start with document element
244: content model nesting level exceeds GRPLVL (X)
245: grand total of content tokens exceeds GRPGTCNT (X)
249: DTDs other than base allowed only if CONCUR YES or EXPLICIT YES
250: end of entity other than document entity after document element
251: X declaration illegal after document element
252: character reference illegal after document element
253: entity reference illegal after document element
254: marked section illegal after document element
255: the X occurrence of Y in the content model for Z cannot be excluded at this point because it is contextually required
256: the X occurrence of Y in the content model for Z cannot be excluded because it is neither inherently optional nor a member of an OR group
257: an attribute value specification must be an attribute value literal unless SHORTTAG YES is specified
258: value cannot be specified both for notation attribute and content reference attribute
259: notation X already defined
260: short reference map X already defined
261: first defined here
262: general delimiter role X already defined
263: number of ID references in start-tag must not exceed GRPCNT (X)
264: number of entity names in attribute specification list must not exceed GRPCNT (X)
265: normalized length of attribute specification list must not exceed ATTSPLEN (X); length was Y
266: short reference delimiter X already specified
267: single character short references were already specified for character numbers: X
268: default entity used in entity attribute X
269: reference to entity X uses default entity
270: entity X in short reference map Y uses default entity
271: no DTD X declared
272: LPD X has neither internal nor external subset
273: element types have different link attribute definitions
274: link set X already defined
275: empty result attribute specification
276: no source element type X
277: no result element type X
278: end of document in LPD subset
279: X declaration not allowed in LPD subset
280: ID link set declaration not allowed in simple link declaration subset
281: link set declaration not allowed in simple link declaration subset
282: attributes can only be defined for base document element (not X) in simple link declaration subset
283: a short reference mapping declaration is allowed only in the base DTD
284: a short reference use declaration is allowed only in the base DTD
285: default value of link attribute cannot be CURRENT or CONREF
286: declared value of link attribute cannot be ID, IDREF, IDREFS or NOTATION
287: only fixed attributes can be defined in simple LPD
288: only one ID link set declaration allowed in an LPD subset
289: no initial link set defined for LPD X
290: notation X not defined in source DTD
291: result document type in simple link specification must be implied
292: simple link requires SIMPLE YES
293: implicit link requires IMPLICIT YES
294: explicit link requires EXPLICIT YES
295: LPD not allowed before first DTD
296: DTD not allowed after an LPD
297: definition of general entity X is unstable
298: definition of parameter entity X is unstable
299: multiple link rules for ID X but not all have link attribute specifications
300: multiple link rules for element type X but not all have link attribute specifications
301: link type X does not have a link set Y
302: link set use declaration for simple link process
303: no link type X
304: both document type and link type X
305: link type X already defined
306: document type X already defined
307: link set X used in LPD but not defined
308: #IMPLIED already linked to result element type X
309: number of active simple link processes exceeds quantity specified for SIMPLE parameter in SGML declaration (X)
310: only one chain of explicit link processes can be active
311: source document type name for link type X must be base document type since EXPLICIT YES 1
312: only one implicit link process can be active
313: sorry, link type X not activated: only one implicit or explicit link process can be active (with base document type as source document type)
314: name missing after name group in entity reference
315: source document type name for link type X must be base document type since EXPLICIT NO
316: link process must be activated before base DTD
317: unexpected entity end while starting second pass
318: type X of element with ID Y not associated element type for applicable link rule in ID link set
319: DATATAG feature not implemented
320: generic identifier specification missing after document type specification in start-tag
321: generic identifier specification missing after document type specification in end-tag
322: a NET-enabling start-tag cannot include a document type specification
324: invalid default SGML declaration
326: entity was defined here
327: content model is mixed but does not allow #PCDATA everywhere
328: start or end of range must specify a single character
329: number of first character in range must not exceed number of second character in range
330: delimiter cannot be an empty string
331: too many characters assigned same meaning with minimum literal
332: earlier reference to entity X used default entity
335: unused short reference map X
336: unused parameter entity X
337: cannot generate system identifier for public text X
339: cannot generate system identifier for parameter entity X
340: cannot generate system identifier for document type X
341: cannot generate system identifier for link type X
342: cannot generate system identifier for notation X
343: element type X both included and excluded
345: minimum data of AFDR declaration must be ""ISO/IEC "" not X
346: AFDR declaration required before use of AFDR extensions
347: ENR extensions were used but minimum literal was not ""ISO
(ENR)"" or ""ISO
348: illegal numeric character reference to non-SGML character X in literal
349: cannot convert character reference to number X because description Y unrecognized
350: cannot convert character reference to number X because character Y from baseset Z unknown
351: character reference to number X cannot be converted because of problem with internal character set
352: cannot convert character reference to number X because character not in internal character set
353: Web SGML adaptations were used but minimum literal was not ""ISO
354: token X can be value for multiple attributes so attribute name required
355: length of hex number must not exceed NAMELEN (X)
356: X is not a valid name in the declared concrete syntax
357: CDATA declared content
358: RCDATA declared content
359: inclusion
360: exclusion
361: NUMBER or NUMBERS declared value
362: NAME or NAMES declared value
363: NUTOKEN or NUTOKENS declared value
364: CONREF attribute
365: CURRENT attribute
366: TEMP marked section
367: included marked section in the instance
368: ignored marked section in the instance
369: RCDATA marked section
370: processing instruction entity
371: bracketed text entity
372: internal CDATA entity
373: internal SDATA entity
374: external CDATA entity
375: external SDATA entity
376: attribute definition list declaration for notation
377: rank stem
379: comment in parameter separator
380: named character reference
381: AND group
382: attribute value not a literal
383: attribute name missing
384: element declaration for group of element types
385: attribute definition list declaration for group of element types
386: empty comment declaration
388: multiple comments in comment declaration
389: no status keyword
390: multiple status keywords
391: parameter entity reference in document instance
392: CURRENT attribute
393: element type minimization parameter
395: #PCDATA not first in model group
396: #PCDATA in SEQ group
397: #PCDATA in nested model group
398: #PCDATA in model group that does not have REP occurrence indicator
399: name group or name token group used connector other than OR
400: processing instruction does not start with name
401: S separator in status keyword specification in document instance
402: reference to external data entity
405: SGML declaration was not implied
406: marked section in internal DTD subset
408: entity end in different element from entity reference
409: NETENABL IMMEDNET requires EMPTYNRM YES
411: declaration of default entity
412: reference to parameter entity in parameter separator in internal subset
413: reference to parameter entity in token separator in internal subset
414: reference to parameter entity in parameter literal in internal subset
415: cannot generate system identifier for SGML declaration reference
416: public text class of formal public identifier of SGML declaration must be SD
417: SGML declaration reference was used but minimum literal was not ""ISO
418: member of model group containing #PCDATA has occurrence indicator
419: member of model group containing #PCDATA is a model group
420: reference to non-predefined entity
421: reference to external entity
422: declaration of default entity conflicts with IMPLYDEF ENTITY YES
423: parsing with respect to more than one active doctype not supported
424: cannot have active doctypes and link types at the same time
425: number of concurrent document instances exceeds quantity specified for CONCUR parameter in SGML declaration (X)
426: datatag group can only be specified in base document type
427: element not in the base document type can't have an empty start-tag
428: element not in base document type can't have an empty end-tag
429: immediately recursive element
430: invalid URN X: missing "":""
431: invalid URN X: missing ""urn:"" prefix
432: invalid URN X: invalid namespace identifier
433: invalid URN X: invalid namespace specific string
434: invalid URN X: extra field
435: prolog can't be omitted unless CONCUR NO and LINK EXPLICIT NO and either IMPLYDEF ELEMENT YES or IMPLYDEF DOCTYPE YES
436: can't determine name of #IMPLIED document element
437: can't use #IMPLICIT doctype unless CONCUR NO and LINK EXPLICIT NO
438: Sorry, #IMPLIED doctypes not implemented
439: reference to DTD data entity ignored
440: notation X for parameter entity Y undefined
441: notation X for external subset undefined
442: attribute X can't be redeclared
443: #IMPLICIT attributes have already been specified for notation X
444: a name group is not allowed in a parameter entity reference in a start tag
445: name group in a parameter entity reference in an end tag (SGML forbids them in start tags)
446: if the declared value is NOTATION a default value of CONREF is useless
447: Sorry, #ALL and #IMPLICIT content tokens not implemented