Markup Validation Service
Check the markup (HTML, XHTML, …) of Web documents
Markup Validation Service
Check the markup (HTML, XHTML, …) of Web documents
The following notes and warnings highlight missing or conflicting information which caused the validator to perform some guesswork prior to validation, or other things affecting the output below. If the guess or fallback is incorrect, it could make validation results entirely incoherent. It is highly recommended to check these potential issues, and, if necessary, fix them and re-validate the document.
Mismatch between Public and System identifiers in the DOCTYPE declaration
This document uses an inconsistent DOCTYPE declaration.
The Public Identifier
-//W3C//DTD HTML 4.01//EN declares the
HTML 4.01 Strict document type, but the associated System Identifier
http://www.w3.org/TR/REC-html4/strict.dtd does not match this document type.
The recommended System Identifier
for HTML 4.01 Strict is http://www.w3.org/TR/html4/strict.dtd.
The safest way to use a correct DOCTYPE declaration is to copy and paste one from the recommended list and avoid editing that part of your markup by hand.
Line 2080,
Column 12:
cannot generate system identifier for general entity "inf"
Sum{ k=0; &inf;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 in URLs".
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-sensitive; &Aelig; and æ are different characters.
If this error appears in some markup generated by PHP's session handling code, this article has 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.
Line 2080,
Column 12:
general entity "inf" not defined and no default entity
Sum{ k=0; &inf;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.
Line 2080,
Column 15:
reference to entity "inf" for which no system identifier could be generated
Sum{ k=0; &inf;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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;Sum{ n=0; &inf; (6n+1)(1/2)n^3 / ( (4^n)(n!)^3 ) }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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;= Sum{ k=1; &inf;; (-1)^(k+1)/( k^2 )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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;= Sum{ k=1; &inf; (-1)^(k+1) /( 36*k^2 - 1 ) }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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;= Sum{ k=1; &inf; 1/( (2*k-1)(2*k+1) ) }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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;+ Sum{ k=1; &inf;; 2^k*(k!)^2/( (2*k+1)! )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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;</blockquote>The Validator found an end tag for the above element, but that element is not currently open. This is often caused by a leftover end tag from an element that was removed during editing, or by an implicitly closed element (if you have an error related to an element being used where it is not allowed, this is almost certainly the case). In the latter case this error will disappear as soon as you fix the original problem.
If this error occurred in a script section of your document, you should probably read this FAQ entry.
Line 2325,
Column 13:
end tag for element "BLOCKQUOTE" which is not open
</blockquote>The Validator found an end tag for the above element, but that element is not currently open. This is often caused by a leftover end tag from an element that was removed during editing, or by an implicitly closed element (if you have an error related to an element being used where it is not allowed, this is almost certainly the case). In the latter case this error will disappear as soon as you fix the original problem.
If this error occurred in a script section of your document, you should probably read this FAQ entry.
Line 2363,
Column 13:
reference to entity "inf" for which no system identifier could be generated
lim{ k->&inf; p_k } = πThis 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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf;<li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2399,
Column 5:
document type does not allow element "LI" here; missing one of "UL", "OL" start-tag
<li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2403,
Column 5:
document type does not allow element "LI" here; missing one of "UL", "OL" start-tag
<li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2412,
Column 4:
document type does not allow element "LI" here; missing one of "UL", "OL" start-tag
<li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2423,
Column 5:
document type does not allow element "LI" here; missing one of "UL", "OL" start-tag
<li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2442,
Column 16:
reference to entity "inf" for which no system identifier could be generated
Sum{ n=0; &inf;; (-1)^n * x^(2*n+1) /( 2*n+1 )! }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.
Line 2080,
Column 11:
entity was defined here
Sum{ k=0; &inf; <li>The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
Line 2513,
Column 6:
end tag for element "UL" which is not open
</ul>The Validator found an end tag for the above element, but that element is not currently open. This is often caused by a leftover end tag from an element that was removed during editing, or by an implicitly closed element (if you have an error related to an element being used where it is not allowed, this is almost certainly the case). In the latter case this error will disappear as soon as you fix the original problem.
If this error occurred in a script section of your document, you should probably read this FAQ entry.
