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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML lang=en-us><HEAD><TITLE>What Makes the WDG HTML Validator Special</TITLE>
<META content="text/html; charset=iso-8859-1" http-equiv=Content-Type><LINK
href="mailto:liam@htmlhelp.com" rev=Made><LINK href="http://www.htmlhelp.com/copyright.html"
rel=Copyright><LINK href="/wdg-html-validator/style.css" rel=StyleSheet
type="text/css"><LINK href="/wdg-html-validator/aural.css" media=aural
rel=StyleSheet type="text/css">
<META content="Liam Quinn" name=author>
<META
content="A discussion of the differences among the WDG HTML Validator, other validators, and lints."
name=description>
<META
content="HTML, HyperText Markup Language, validator, validate, validation, HTML validator, HTML validation, differences, difference, check, WDG, Web Design Group"
name=keywords>
<META content="MSHTML 5.00.2014.210" name=GENERATOR></HEAD>
<BODY>
<H2><IMG alt="The Web Design Group" height=83
src="/wdg-html-validator/wdglogo1.gif" width=250></H2>
<H1>Validator Differences</H1>
<P>The <A href="/wdg-html-validator/"><ABBR class=initialism
title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator</A> is similar in many
ways to the <A href="http://validator.w3.org/">W3C HTML Validation Service</A>
and the (now unavailable) <A href="http://www.webtechs.com/">WebTechs</A>
Validation Service. The <ABBR class=initialism
title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator does not use any source
code from the other validators, but all three validators use <A
href="http://www.jclark.com/">James Clark</A>'s <A
href="http://www.jclark.com/sp/nsgmls.htm">nsgmls</A> internally. While the
three validators use different versions of nsgmls, the errors from all three
should be the same in most cases. However, some differences may arise:</P>
<UL>
<LI>
<P>The W3C HTML Validation Service and WebTechs Validation Service both use
error messages directly from nsgmls. The <ABBR class=initialism
title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator differs in that it
uses custom error messages for common errors in <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> validation.</P>
<LI>
<P>Only the <ABBR class=initialism title="Web Design Group">WDG</ABBR> <ABBR
class=initialism title="HyperText Markup Language">HTML</ABBR> Validator
supports <A href="/doc/wdg-html-reference/html40/">HTML 4.0</A>'s
hexadecimal character references since the other validators use an older
version of nsgmls. The other validators will give false errors of the form
"XA0 is not a function name".</P>
<LI>
<P>Unlike the other validators, the <ABBR class=initialism
title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator supports <A
href="/wdg-html-validator/charset.html">character
encodings</A> other than just ISO-8859-1. When validating documents in
encodings such as UTF-8, the other validators typically give false errors of
the form "non SGML character number 136". The <ABBR class=initialism
title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator currently supports <A
href="/wdg-html-validator/supported-encodings.html"
title="Character Encodings Supported by the WDG HTML Validator">40 character
encodings</A>, with more encodings added as demand dictates.</P>
<LI>
<P>Another source of discrepancy in the errors reported by the validators is
WebTechs' default behavior of translating "&" to "&amp;" in <ABBR
class=initialism title="Uniform Resource Locator">URL</ABBR>s. This hides the
common error of not escaping the ampersand in <ABBR class=initialism
title="Uniform Resource Locator">URL</ABBR>s, for example in <STRONG
class=html><A HREF="foo.pl?chapter=1&section=2"></STRONG>. The <ABBR
class=initialism title="Web Design Group">WDG</ABBR> <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> Validator does not hide this
error since browser problems with the unescaped ampersand are more common than
browser problems with the escaped ampersand. In the preceding example, the
widely used Netscape Navigator 3.<VAR>x</VAR> would treat <STRONG
class=html>&section</STRONG> as "ion" and would not correctly follow the
link. If valid <ABBR class=initialism
title="HyperText Markup Language">HTML</ABBR> is used, <STRONG
class=html><A HREF="foo.pl?chapter=1&amp;section=2"></STRONG>, the
only known browser to have problems is the lightly used testbed browser <A
href="http://www.w3.org/Amaya/">Amaya</A>.</P></LI></UL>
<P>The three validators all differ significantly from other checking tools such
as <A href="http://www.cre.canon.co.uk/~neilb/weblint/">Weblint</A> and <A
href="http://www.htmlvalidator.com/">CSE 3310 HTML Validator</A>. (Despite its
name, the latter is not a true "validator.") The three online validators check
documents against a <EM>document type definition</EM>--a published,
machine-readable document that facilitates an <EM>objective</EM> check of syntax
against <ABBR class=initialism title="HyperText Markup Language">HTML</ABBR>
standards. On the other hand, lints are <EM>subjective</EM>; they provide a more
cursory syntax check while adding stylistic checks, such as warning about poorly
supported features. Lints are useful tools, but they are not substitutes for
<ABBR class=initialism title="HyperText Markup Language">HTML</ABBR>
validation.</P>
<DIV class=footer>
<P class=toolbar><A href="/wdg-html-validator/">Validate by
<ABBR class=initialism title="Uniform Resource Locator">URL</ABBR></A> ~ <A
href="/wdg-html-validator/upload.html">Validate by file
upload</A> ~ <A
href="/wdg-html-validator/direct.html">Validate by direct
input</A></P>
<DIV class=footer>
<ADDRESS>Developed and maintained by <A href="http://htmlhelp.com/~liam/">Liam
Quinn</A> <<A
href="mailto:liam@htmlhelp.com">liam@htmlhelp.com</A>></ADDRESS>
<ADDRESS>Debian Package maintained by Jaldhar H. Vyas <<A
href="mailto:jaldhar@debian.org">jaldhar@debian.org</A>></ADDRESS>
<P class=toolbar><A href="http://htmlhelp.com/"><IMG alt="Web Design Group ~ "
height=40 src="/wdg-html-validator/wdglogo-small.gif" width=105></A><A
href="/doc/wdg-html-reference/html40/">HTML 4.0 Reference</A> ~
<A href="/doc/wdg-html-reference/wilbur/">HTML 3.2 Reference</A> ~
<A href="/doc/wdg-html-reference/css/">Cascading Style Sheets Reference</A></P>
<P class=copyright><A href="http://htmlhelp.com/copyright.html">Copyright </A>
1998-99 Liam Quinn. All rights reserved.</P></DIV>
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