XHTML bridges the gulf between HTML and XML

But until now, the gulf between XML and HTML has restricted XML's spread on the Web. The two are both mark-up languages. They speak very differently. It has taken an ingenious new language called XHTML to bring them together.

HTML mixes data and presentation simplistically together, not caring what's in a heading or a list. Partly because of this, HTML is an inflexible monolithic standard - an inflexible monolithic standard that millions of browsers understand right now, and on which a powerful new medium has been built.

XML is a language for describing sets of data, and it has already been enthusiastically adopted by leading-edge software engineers, document publishers and people who exchange data. It leaves a separate acronym - sorry, language - called XSL to take care of presentation. And unlike HTML, XML can be extended with sets of tags defined by the creators of an XML document. But it's very different from HTML. Many of the browsers out there today don't understand it; many of the Web developers are equally mystified.

XHTML brings XML to today's Web, relatively painlessly and without the five-year wait for everyone to adopt XML-compliant browsers. XHTML takes many of the merits of XML and plugs them into a revised version of the current HTML 4.0 specification. It's a stricter, neater HTML dialect, but you'll recognise it instantly if you know HTML. It lets you "modularise" your site mark-up, explaining to browsers and other Web-readers just what tags each page requires. You can also include snippets of non-HTML XML in your XHTML documents wherever that's appropriate. And XHTML lets you define your own tags in a way that any XML-compliant browser will understand. Think of XHTML as HTML 5.0; just remember that it's a particularly significant and powerful upgrade.

It's also one of those upgrades that's beautifully compatible with previous versions. Build your pages as XHTML, and most browsers will still understand them just fine.

XHTML does ask you to change your current HTML documents, but it doesn't ask the world. Your documents will need some alien-looking new headers; you must put quote marks around tag attributes; the humble break tag, <br>, now becomes <br />, and so on. But a good search-and-replace tool will take care of much of the XHTML transformation. And Web sites that already create pages out of templates and databased content using code-based editing tools will find the transformation particularly easy.

That copy of FrontPage on your PC won't create XHTML pages. But a combination of standard text-based Web editors and the tools detailed below will let you start building XHTML pages.

XHTML became an official W3C recommendation back in January 2000. With that recommendation, the Web's past and its future were officially linked.

This site has made a practice of questioning alleged "breakthroughs" in the Web industry. But XHTML really does deserve to be taken seriously right now.