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<barbelith> is not a namespace, it's an element. http://www.w3.org/1999/xhtml is a namespace.
Essentially, a namespace is an 'abstract container' where the vocabulary for the XML file is stored. All the elements of valid XHTML exist in that namespace. <barbelith> does not, so it isn't valid XHTML.
Adding a <barbelith> tag makes it invalid XHTML. XHTML is HTML that follows the basic rules of XML: correctly nested elements, case-sensitive elements (which are all, in the case of XHTML, lowercase), all elements must be closed, all elements must exist in the namespace.
Does that help at all?
As a webdesigner, you need to be starting with XHTML, but it's almost identical to the HTML you'll know. Most of the problems you'll have will be related to closing tags that you're not used to, or closing single tags (eg <br /> rather than <br>. Not only is it the way forward - and, with any luck, forwards-compatible - but it makes more sense, and is a lot more consistent, semantically.
Regarding XML: you need to know it exists, and have the vaguest idea of how it works. The most common place you'll encounter it, at the small/personal site level is RSS or Atom. You're probably not going to need to know stuff like XSLT, or XPath, unless you get more into web programming rather than design/layout.
If any of that was unclear, just ask - and hopefully, I won't have gone too far over your head. |
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