Why XHTML™?

Or, Why not HTML?

The Document Type Definition (DTD) or, DOCTYPE, should be the first thing considered when construction begins. Which DTD should be used.

HTML? Or, XHTML?

Numerous texts have been offered. “The perils of using XHTML properly | 456 Berea Street” published January 18, 2005 by Roger Johansson, “HTML or XHTML?” published November 2, 2005 by Robert Nyman, “XHTML advocates considered erroneous” published November 18, 2005 by Anne van Kesteren and, “The Road to XHTML 2.0: MIME Types” which was published March 19, 2003 by Mark Pilgrim.

Lastly, “Differences with HTML 4” or, when using XML, ongoing • Drop the <!DOCTYPE>” published December 19, 2005 by Tim Bray.

It’s a conundrum, isn’t it.

Therefore, in the spirit of Flying Monkeys from Borneo, the following was composed for those who want to follow those with Knowledge. You’ve read code. You’ve followed examples set by “The Old Professionals”. Still. There are some aspects of fundamental web development that are unfathomable when starting-up.

The following were selected from collected sites which meet web standards. I haven’t included all of the sites noted or referenced on The Elementary Group Standards for various reasons, e.g., non-standards compliance.

And, in no particular random order.

[S]

1 456 Berea Street | Articles and news on web standards, accessibility, and usability
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="A website focused on web standards, accessibility, usability and other things related to web development and web design.">

2 And all that Malarkey
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="Malarkey is Andy Clarke, a UK based designer with a passion for design, CSS and accessibility. This is his personal site, And All That Malarkey." />

3 Tantek's Thoughts
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-us" lang="en-us">
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE"/>

4 Jeffrey Zeldman Presents The Daily Report
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
<meta name="description" content="CSS, XHTML, front end design. Jeffrey Zeldman Presents The Daily Report: web design news and information since 1995." />

5 A List Apart: A List Apart
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<meta name="description" content="A microformat for book printing and a call to simplicity in web design and development" />
[Note: A List Apart’s description describes the articles on it’s index page which happens to be it’s home page.]

6 mezzoblue § design, typography, and the web: live from vancouver, b.c., canada
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" id="www-mezzoblue-com">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="mezzoblue: the daily weblog of dave shea, a web designer in vancouver, b.c., canada." />

7 meyerweb.com
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="description" content="NONE" />

8 Anne’s Weblog about Markup & Style
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
 [Note: Mr. van Kesteren's quote.]
<meta http-equiv="Content-Type" content="NONE" />
<meta name="description" content="NONE" />
[Note: No <head>, no <html> and no <body>.]

9 stu nicholls | CSS PLaY | experiments with cascading style sheets
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
<meta name="Description" content="CSS ~ Cutting edge Cascading Style Sheets. Experiments in CSS" />

10 satzansatz
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="Description" content="NONE" />

11 /* Position Is Everything */ — Modern browser bugs explained in detail!
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="Advanced CSS demos and bug reports" />

12 molly.com
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE"/>

13 SimpleBits
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="Hand-crafted web sites, pixels and text by Dan Cederholm." />

14 css Zen Garden: The Beauty in CSS Design
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="A demonstration of what can be accomplished visually through CSS-based design." />

15 Design Meme
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="description" content="NONE" />

16 ShaunInman.com
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="NONE" />

17 Stopdesign
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="A design consultancy led by Founder and Principal, Douglas Bowman, based in San Francisco, California, Stopdesign specializes in a simple, beautiful aesthetic, balance of form and function, and highly flexible design." />

18 Airbag Industries
<?xml version="1.0" encoding="iso-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="description" content="Airbag Industries, LLC is a consultancy that aids businesses with their Internet related concerns." />

19 Adactio: Journal
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<meta name="description" content="Adactio is the website of Jeremy Keith, a web developer living in Brighton in southern England." />

20 {Non Troppo}-{not, um, exactly | a personal weblog}
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<meta name="description" content="NonTroppo - not, um, exactly | a personal weblog by Ian Andolina" />

21 Stylegala - Web Design Publication
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<meta http-equiv="Content-type" content="text/html; charset=ISO-8859-1" />
<meta name="description" content="NONE" />

22 Andy Budd::Blogography
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

23 westciv :: home
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="Web standards resources - tutorials, software and courses for CSS, HTML/XHTML and accessibility" />

24 Robert’s talk
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/DTD/strict.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="Description" content="Here you will find posts about news, trends and developing for internet, mainly focusing on browsers and web user interfaces.">

25 [Previous] Veerle's blog
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="description" content="NONE" />

25 [Present] Veerle's blog 2.0 - Webdesign - XHTML CSS | Graphic Design
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="description" content="Veerle's blog 2.0. Webdesign talk - XHTML CSS , Graphic Design tutorials." />

26 as days pass by
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="description" content="NONE" />

27box of chocolates
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

28 Subtraction 7.0
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

29 Simon Willison's Weblog
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

30 arkitrave :: architecture, web design, and stuff » General
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

31 [Previous] The Web Standards Project
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="NONE" />
<meta name="description" content="NONE" />

31 [Present] The Web Standards Project
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="description" content="The Web Standards Project is a grassroots coalition fighting for standards which ensure simple, affordable access to web technologies for all." />

32 Accessify.com - all the tools, links and resources you'll ever need to make your web site accessible.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

33 Juicy Studio: No artificial additives
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en-gb">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="description" content="NONE" />

34 Web Standards with Imagination: Dustin Diaz
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en:us">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="description" content="NONE" />

35 Boxes & Arrows
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8;" />
<meta name="description" content="NONE" />

36 W3C QA - The QA Toolbox
<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<meta name="Description" content="W3C QA - repository of QA tools and validation software at W3C" />

37 Blue Flavored - The Official Blog of Blue Flavor Experience Design
<?xml version="1.0" encoding="iso-8859-1"?>
<DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

38 Asterisk | D. Keith Robinson’s Web Design Blog.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="Asterisk* - A Web Design Blog by D. Keith Robinson" />

39 Left Justified
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Language" content="en-au" />
<meta name="description" content="NONE" />

40 Clearleft Web Design and Accessibility Consultants
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

41 Contentious
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"<
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="NONE" />

42 QuirksMode
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<meta name="description" content="NONE" />
[Note: SHTML Version]

42a QuirksMode - for all your browser quirks
<html lang="en">
[Note: W3C DOM Version]

43 CollyLogic | Illogical Waffle
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"/>
<meta name="description" content="CollyLogic. The ever-so engaging blog of Simon Collison, lead web developer at Agenzia, and founder of You Are Here Visual Arts, Nottingham UK" />

44 The KuraFire Network
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<meta name="description" content="Growing into Website design with XHTML and CSS, explaining how to use CSS for powerful layouts" />

45 GUUUI - The Interaction Designer's Coffee Break
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
<meta name="description" content="GUUUI - the interaction designer's coffee break, with daily postings and quarterly articles about interaction design" />

46 Coudal Partners
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
<meta name="description" content="NONE" />

47 Digital Web Magazine
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
<meta name="description" content="Digital Web Magazine" />

48 Creative Commons
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<meta name="description" content="NONE" />

49 Email Newsletter and List Management Software for Web Designers - Campaign Monitor
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<meta name="description" content="Campaign Monitor - email newsletter and list management software built for web designers to send their campaigns, track the results and manage their subscribers." />

50 The Guild of Accessible Web Designers
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
<meta name="Description" content="Welcome to the Guild of Accessible Web Designers" />

Or,

What DOCTYPE was used?

None = 1
HTML 4.01/Strict = 3
HTML 4.01/Transitional = 3
XHTML 1.0/Strict = 20
XHTML 1.0/Transitional = 19
XHTML 1.0/Transitional + XML 1.0 = 1
XHTML 1.1 = 3

Fifty sites. Fifty sites representing “Old Web Development Professionals”.

Very Unstandard standard, isn’t it.

It’s simple, really. Monkey whomsoever you'd like. Though, whichever’s chosen, we recommend using “Strict” for its benefit of rendering markup by browsers in a standards mode. [ws] DOCTYPE And Browser Modes illustrates this.

However, “ XHTML is not for Beginners ” published December 5, 2005 by Lachlan Hunt is what anyone learning Structural Markup Languages should follow.

And, if you should choose XHTML, XML schema validator by Christoph Schneegans is highly recommended.

Corrigenda

This site uses HTML 4.01/Strict utilizing the well-formedness requirements of “XHTML™ 1.0 The Extensible HyperText Markup Language (Second Edition): A Reformulation of HTML 4 in XML 1.0.” (excepting those XHTML-specific requirements found Appendix C, i.e., C.1, C.2 and C.3). This decision was based on three unassuming facts.

XHTML 1.0 is not forward compatible; XHTML 2.0 will not be backwards compatible.
Serving XHTML as application/xhtml+xml does’t work in IE.
HTML 5 continues to be written for strict adherence to backwards compatibility.

[30 March 2006]

The Elementary Standards: A Compendium of articles, tutorials and reference material regarding Web Standards, HTML and CSS Copyright ©2005-2008. All work is published under a Creative Commons License. All Rights Reserved.