ID "FOO" already defined-
You have defined the id/name "FOO" more then once.
You will also get a message telling you where it was first defined.
Be aware that this message may be the result of an ambiguity in
the specification. While user-agents must treat values of the id
attribute as case-sensitive, they must still be case-insensitive
unique in the document. See Section
12.2.1 Syntax of anchor names in the HTML
4.01 Recommendation for further information.
-
Unterminated comment. The position indicator points to the very
end of the file, where the problem was detected; to find the beginning
of the comment, try searching for the last occurrence of "<!--"
in the document.
-
Unterminated comments again. This time, you have a case like:
<!-- This is the first unterminated comment
>
<!-- This is the second one >
The validator (correctly) interprets the "--"
in the second comment as terminating the first comment, and then
interprets the text of the second comment as text between comments,
which is not allowed.
-
Most likely an invalid comment of the form "<!invalid
comment>"; the validator is (correctly) attempting to
interpret it as an SGML markup
declaration.
an attribute value must be a literal unless
it contains only name characters-
You have an attribute whose value needs to be in quotes. If an
attribute value contains any character other than letters, digits,
hyphens and periods, it must be enclosed in double quotes (single
quotes would also be OK from an SGML standpoint,
but some browsers don't recognize them).
character "X" not allowed in attribute
specification list-
The validator has found a character inside an HTML
tag that isn't allowed there. This usually means you didn't put
an attribute value in quotes when necessary. It also probably means
that the character in question is not allowed in the value of the
attribute at all, or you would have received the previous
error instead. See below for more
information.
You can also get in trouble by forgetting the closing quote on
an attribute. For instance:
<img src="http://foo.com/fred.gif>
<img src="http://foo.com/joe.gif>
The validator will (correctly) interpret this as a src
value of "http://example.com/fred.gif> <img
src=", and then choke on the following ":".
In this case, the position indicator in the error message may be
several lines below the line with the missing quote.
length of attribute value must not exceed
LITLEN less NORMSEP (1022)-
This usually occurs in conjunction with the previous
error. It almost always means that you've forgotten a closing
quote on an attribute value. For instance, in:
<img src="fred.gif>
<!-- 50 lines of stuff -->
<img src="joe.gif">
The "src" value for the first <img>
is the entire fifty lines of stuff up to the next double quote,
which probably exceeds the SGML-defined
length limit for HTML
string literals. Note that the position indicator in the error message
points to where the attribute value ended — in this
case, the "joe.gif" line.
element "FOO" undefined-
You've used an unknown tag (represented here by "FOO").
Make sure the DTD
indicated by your DOCTYPE actually includes
this element.
If the tag in question is a frame-related tag you must use the
"Frameset" DTD, and
if you use (deprecated) physical markup ("FONT" and friends) you
must use the "Transitional" DTD.
document type does not allow element "FOO"
here-
Straightforward, but not terribly informative. There are several
different mistakes that will generate this error message:
- Using an unknown tag. In this case, the next error will be
element "FOO" undefined".
- Using a tag in the wrong place. For instance,
<table><td>blah</table>
will cause this error. The trick here is that a <table> element cannot directly
contain <td> elements; it contains
one or more <tr> elements which
in turn contain <td> elements.
The above example should be <table><tr><td>blah</table>.
document type does not allow element
"FOO" here; assuming missing "BAR" start-tag-
Similar to the previous error, but
more specific: in this case, you have a "FOO" element
that is not contained in a "BAR" element when "FOO"
is not allowed outside of "BAR". Some of the most common
causes of this error are:
The validator has inserted a "BAR" start tag where
it thinks there needs to be one; it will probably complain later
on that the corresponding end tag is also
missing.
there is no attribute "FOO" for
this element-
You have used an attribute with an element that is defined not
to have that attribute. This is most commonly caused by using vendor-specific
attributes without setting the document type appropriately.
"FOO" is not a member of the
group specified in the declared value of this attribute-
Similar to the previous error; this
time, you're using an attribute that is defined for the element,
but with a value that isn't defined for the attribute. For instance,
the Netscape extension <img align="absmiddle">
will cause this error; "absmiddle" is
not one of the allowed values for the "align"
attribute of <img> (unless, of
course, you provided a Netscape document type).
If you're using the Netscape document type, the "border"
attribute of "<table>" can cause
this error.
This error can also be caused, oddly enough, by missing close
quotes on attribute values. For instance, given:
<img src="fred.png> <img src="joe.png>
The validator will (correctly) see a src
attribute of "fred.png> <img src=",
and then try to interpret joe.png as
an attribute of <img>.
syntax of attribute value does not conform
to declared value-
Yet another attribute error; this time, the attribute in question
was defined to take a numeric value, or an SGML identifier
value, and you used a character that doesn't match what it was expecting.
One potentially annoying source of this error is the width
attribute on the td element. Whether
intentionally or by oversight, the HTML 3.2 DTD defines this attribute
to have a value type of NUMBER, which
means that <td width="50%"> is
not allowed.
value of attribute "FOO" invalid:
"#" cannot start a name-
A special case of the previous error;
the attribute in question is defined to take as value an SGML NMTOKEN,
a name token, which must begin with a letter.
"FOO" is not a member of a
group specified for any attribute-
Another attribute error, this time referring to an "abbreviated"
(minimized) attribute. SGML allows
you to omit the name of an attribute if the attribute value is unambiguous.
For instance, "<img ismap>" is
actually an abbreviation of <img ismap="ismap">.
The validator has found something that looks like an abbreviated
attribute but doesn't match the value of any attribute for this
element. For instance, a typo like "<img
isnap>" would produce this error.
A missing close quote on a previous attribute value can also trigger
this error if the next quote it finds is followed by something that
looks like an abbreviated attribute; for instance,
<img src="fred.png><img src="joe.png>
would produce this error, referring to the "attribute value" joe.png.
required attribute "FOO" not
specified-
You left off a required attribute of the indicated element. The
most common such omitted attribute is the alt
attribute of the area or img element; browsers will typically use these
to build a menu equivalent to your client-side image map if the
user has disabled image loading, so you'll want to use a meaningful
value here.
end tag for "FOO" omitted, but
its declaration does not permit this-
You forgot to close something. "FOO" is the element
you forgot to close (and the next message, "start
tag was here" points to the particular instance of "FOO"
in question); the positional indicator points to where the validator
expected you to close the element. There are a few common ways that
this can happen:
-
You've put something inside the "FOO" element that
isn't allowed there. For instance,
<ul><li><h4>fake
font change</h4></li></ul>
will cause this error, since headers aren't allowed inside
<ul> elements; the validator assumes
that you meant to close the <ul>
before opening the <h4>.
- Interlocked elements. For instance,
<b><i>nope</b></i>
will cause this error. HTML
requires that you close elements inside-out — that is, the
last element you opened is the first element you should close.
In this example, you'd have to close the <i> before the <b>.
- Unclosed
<a> tags. Yes, even
<a name="foo"> has to have a
corresponding </a>. Note that
an empty <a name="foo"> element
won't be recognized by some browsers; be sure to put at least
a word or two inside the <a>.
- Having unadorned text where the validator was expecting a sub-element
of "FOO". For instance,
<dl>fake
indent</dl> will produce this error, since
inside a <dl>, the validator
only expects to see <dt> and
<dd> elements (i.e. you can't just
put text in there).
-
A tag of the form <table width=100%>.
The previous error should have been that the "%"
was "not allowed in
attribute specification list".
What's happening here is that, in trying to get past the "%", the validator has become confused
and thinks the "%" is inside
the <table>…</table>,
thus triggering the error message for the previous reason. This
error will likely be followed by mistaken complaints that your
<tr> elements are "not allowed here",
plus a complaint about your </table>
end tag. The solution is to put the attribute value in quotes;
ie. <table width="100%">.
In general, you should always explicitly close all elements
and quote all attribute values!
end tag for element "FOO" which
is not open-
The validator found an end tag, represented here by "FOO",
without a corresponding start tag. This frequently occurs in conjunction
with the previous error. For instance,
given <b><i>nope</b></i>,
the validator will insert a </i>
before the </b>, and then will
find the </i> after the </b> and will have nothing to match
it with.
A subtle variation of this is <p><h4>fake font change</h4></p>.
<h4> elements are not allowed
inside <p> elements, but since
HTML allows you to omit
the </p> end tag for paragraphs
(unlike XHTML),
the validator assumes that you meant <p></p><h4>fake
font change</h4></p>, in which case the
final </p> is indeed superfluous.
This error can also be caused by incorrectly supplying an end
tag for "empty" elements like <hr>,
<br> or <img>.
This is why they are written <hr />,
<br />, and <img
/> in XHTML.
end tag for "FOO" which is
not finished-
You have a "FOO" element, but you have omitted some
required sub-element of it. For instance, a table
with no tr's would cause this error.
start tag for "FOO" omitted,
but its declaration does not permit this-
The validator expected you to start a "FOO" element
at the indicated point. This probably means you've put unadorned
text somewhere it isn't allowed; for instance, <ul>fake
indent</ul> will cause this error.
unknown entity "FOO"-
The validator has found an entity (something like &this;)
that it doesn't recognize. There are a few possibilities:
-
A reference to a URL
that uses "&" as a separator
between parameters, such as "http://example.com/cgi-bin/prog?x=1&y=2".
To solve this problem, simply replace all the &'s in attribute values with &
(user agents will convert them back before following the links).
Another way to get around this problem is for the author of
the CGI program
to allow a different value to be used between arguments, like
";" or "|",
which would allow the link to be coded as e.g. <a
href="http://example.com/cgi-bin/prog?x=1;y=2">
- An unterminated entity; for instance, "
this&that" for "this&that",
which the validator (correctly) interprets as a request for the
entity "&that;". Technically, any non-alphanumeric
character (such as a space) will suffice to terminate the entity,
but some browsers get this wrong; the safest thing to do is to
terminate all entities with a semicolon, turning our example into
"this&that".
- The entity
" in conjunction
with the HTML 3.2
DOCTYPE. This entity was accidentally
omitted from the most recent version of the HTML 3.2 DTD. You should be able
to ignore this error safely, though if you wish, you can replace
" with the equivalent character
entity ".
non SGML
character number ###-
You have used an illegal character in your text. HTML
uses the standard UNICODE Consortium
character repertoire, and it leaves undefined (among others) 65
character codes (0 to 31 inclusive and 127 to 159 inclusive) that
are sometimes used for typographical quote marks and similar in
proprietary character sets. The validator has found one of these
undefined characters in your document. The character may appear
on your browser as a curly quote, or a trademark symbol, or some
other fancy glyph; on a different computer, however, it will likely
appear as a completely different character, or nothing at all.
Your best bet is to replace the character with the nearest equivalent
ASCII character, or to use an appropriate character entity.
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.
cannot generate system identifier for entity
"HTML"-
Your DOCTYPE declaration contains
a public identifier that the validator does not recognize. See the
discussion of DOCTYPE
for an explanation of what's happening, and what public identifiers
the validator recognizes.
missing a required sub-element of "FOO"-
The element "FOO" is defined to require one
or more sub-elements. One example is tr
which requires one or more td or th
elements.
start tag was here-
Not an error, but rather a pointer to the start tag of the element
the previous error referred to.
text is not allowed here; try wrapping
the text in a more descriptive container-
The document contained bare text where an element was expected.
For instance, you must wrap text in <p>
if it appears directly inside the <body>.
This error may also indicate an unquoted attribute value containing
a reserved character (such as "/") which
terminates the attribute. The net effect is that the rest of the
attribute value appears to be plain text, outside any element, to
an SGML parser.
value of attribute "FOO" cannot
be "BAR"; must be one of "FOO", "BAR",
"BAZ"-
An attribute was specified to contain one of a set of predefined
values and you have used a value that is not in that set. The error
message tells which attribute value was unknown and the possible
legal values for this attribute.
character "FOO" not allowed in
attribute specification list possibly caused by a missing quotation
mark ending a previous attribute value-
A character that is illegal in the attribute list for a particular
attribute was encountered. It's is likely that this is a result
of a missing quote character on a previous attribute value.
duplicate specification of attribute "FOO"-
You have specified an attribute more than once. For instance,
you have used the "height" attribute
twice on the same "img" tag.
invalid attribute value-
The value of this attribute is not a legal value for attributes.
For instance, the attribute cannot be the empty string. This is
distinct from errors related to illegal values for a specific attribute.
an attribute specification must start
with a name or name token-
An attribute name (and some attribute values) must start with
one of a restricted set of characters. This error usually indicates
that you have failed to add a closing quotation mark on a previous
attribute value (so the attribute value looks like the start of
a new attribute) or have used an attribute that is not defined (usually
a typo in a common attribute name).
-
There is a syntax error in an SGML
Comment Declaration. This may be caused by too many or too few hyphens
"-" or that you have included an invalid character in the comment.
The next message will be "comment declaration started here".
element "FOO" not
allowed here; assuming missing "BAR" start-tag-
The referenced element "FOO" isn't allowed in the context
it occurs in, but it would be if it was wrapped in a "BAR"
element. The Validator has assumed that you have forgotten to add
a "BAR" start tag and continued validation as if it was
there. You should check if this is the case and insert the proper
tag.
