Resources ⮞ HTML & xHTML
Error: JavaScript is needed to render this site: please enable it.
This gives information about the HTML and xHTML hypertext markup languages.
NB: unless otherwise indicated, ‘HTML’ on this page denotes both HTML and xHTML.
HTML Specifications
HTML recommendations (i.e. specifications) are issued by the W3C (World-Wide Web Consortium).
Beginning in May 2019, however, HTML and DOM standards are first established by the WHATWG community. The specifications are:
W3C Standards
HTML 2.0: mainly of historical interest.
HTML 3.2: roughly supported by IE3 and NN3; well supported by Opera 3.62.
HTML 4.00: superceded by HTML 4.01.
HTML 4.01: supported, poorly, by NN4; better by IE4; better still by IE5; well supported by IE6+, Mozilla 1.7+ (and its progeny - Camino, Firefox, SeaMonkey, etc.), NN7+, Safari, and Opera 7+.
HTML 5 and XHTML 5: supported fairly well by the most modern browsers. Related HTML 5 documents include A vocabulary and associated APIs for HTML and XHTML, HTML5 differences from HTML4, HTML5: Edition for Web Authors, HTML+RDFa 1.1, HTML Microdata, HTML Canvas 2D Context, and Polyglot Markup: HTML-Compatible XHTML Documents.
There is also a related HTML 5.1 2nd Edition specification, now obsoleted by the 5.2 recommendation.
There is also a related HTML 5.2 and XHTML 5.2 specification.
xHTML 1.0: accepted by older browsers except NN1-NN3.
xHTML 1.1: modularized xHTML 1.0 Strict, with poorer support by legacy browsers than xHTML 1.0. A related document is the W3C Note xHTML+SMIL Profile, integrating a SMIL 2.0 subset with xHTML, with modules for animation, content control, media objects, timing & synchronization, time manipulations, and transition effects.
xHTML 2.0: working note of xHTML 2.0 standard.
WHATWG Standards
- HTML and xHTML Living Standard: HTML/xHTML standards; see also WHATWG DOM standard.
- Compatibility Living Standard: minimal non-standard CSS and DOM standards.
- Console Living Standard:
consoleJavaScript methods. - DOM Living Standard: DOM standard.
- Quirks Mode Living Standard: legacy browser support.
NB: no browser completely and correctly implements any version of HTML; modern browsers, however, come very close.
NB: some modern browsers implement the specifications more correctly if a DOCTYPE is specified in the HTML file [more⮞.
HTML Validators
Validators check to see whether HTML and xHTML files are syntactically correct, i.e. are written in accordance with the specifications.
Some validators are:
- A Real Validator: software to validate files off-line, using Windows. Trialware. Recommended.
- W3C Validator: an on-line validation service. Free.
- WDG Validator: an on-line validation service. Free.
- WDG Off-line Validator: software to validate files off-line, using Unix. Free.
NB: links to various validators and code checkers can be found on the WDG site.
Caution: some vendors sell code checkers but wrongly call them validators. [more⮞
HTML Code Checkers
Code checkers (sometimes called syntax checkers or lint programs) check for problems in HTML code. Some checks are similar to those that validators do. Other checks are beyond the scope of validators, e.g. checking for missing files, missing anchor tags, missing end tags, broken links, browser compatibility problems, browser accessibility problems, etc.
Some HTML code checkers are:
- CSE’s HTML Validator. Also a CSS code checker. A free ‘lite’ version is available.
- LinkScan.
- Talicom’s HTML Power Tools. Not recently updated.
- W3C Link Checker: an on-line service to find broken links. Free.
- W3C mobileOK Checker: an on-line service to find possible problems in sites for mobile devices. Free.
- Weblight.
- Xenu’s Link Checker. Free.
NB: links to various validators and code checkers can be found on the WDG site.
Caution: some vendors sell code checkers but wrongly call them validators. [more⮞
