Skip to Content
HTML & XHTML: The Definitive Guide, 6th Edition
book

HTML & XHTML: The Definitive Guide, 6th Edition

by Chuck Musciano, Bill Kennedy
October 2006
Intermediate to advanced
680 pages
21h 44m
English
O'Reilly Media, Inc.
Content preview from HTML & XHTML: The Definitive Guide, 6th Edition

Well-Formed Documents and XHTML

XHTML is HTML's prissy cousin. What would pass most beauty contests as a very proper and complete HTML document, done according to the book and including end-paragraph tags, might well be rejected by the XML judges as a malformed file.

To conform with XML, XHTML insists that documents be "well formed." Among other things, that means that every tag must have an ending tag—even the ones like <br> and <hr> for which the HTML standard forbids the use of an end tag. With XHTML, the ending is placed inside the start tag: <br />, for example. [Handling Empty Elements, 16.3.3]

It also means that tag and attribute names are case-sensitive and, according to the current XHTML standard, must be in lowercase. Hence, only <head> is acceptable, and it is not the same as <HEAD> or <HeAd>, as it is with the HTML standard. [Case Sensitivity, 16.3.4]

Well-formed XHTML documents, like HTML standard ones, must also conform to proper nesting. No argument there. [Correctly Nested Elements, 16.3.1]

In their defense, the XML standard and its offspring, XHTML, emphasize extensibility. That way, <p> can mean the beginning of a paragraph in HTML, whereas another variant of the language may define the contents of the <P> tag to be election-poll results that display quite differently—perhaps in tabular form, with red, white, and blue stripes and accompanying patriotic music.

We will discuss this further in Chapters 15 and 16, in which we detail the XML and XHTML standards (and the ...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.

Read now

Unlock full access

More than 5,000 organizations count on O’Reilly

AirBnbBlueOriginElectronic ArtsHomeDepotNasdaqRakutenTata Consultancy Services

QuotationMarkO’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.
Julian F.
Head of Cybersecurity
QuotationMarkI wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.
Addison B.
Field Engineer
QuotationMarkI’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.
Amir M.
Data Platform Tech Lead
QuotationMarkI'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Mark W.
Embedded Software Engineer

You might also like

HTML and CSS: Visual QuickStart Guide, 9th Edition

HTML and CSS: Visual QuickStart Guide, 9th Edition

Joe Casabona

Publisher Resources

ISBN: 0596527322Errata Page