Structure, presentation, and behavior
When split up this way, your sites will contain three types of text files:
When you do this, it becomes straightforward to make changes to your siteeven changes with site-wide effects.
Divs and spans
If you're used to the classic style of HTML, where you threw everything into tables and played with spacer GIFs until it all fell into more-or-less the layout you wanted, some of this will be new to youso here's a quick overview to bring you up to date.
XHTML contains two tags that are just starting to get the attention they deserve: <div> and <span>. They're used to break up your content into semantic chunks, that is, chunks that have a similar meaning. Things inside a single table cell or paragraph may or may not have anything in common, but the content within each <div> and <span> should.
Why use one over the other? A <div> is a block-level element, that is, there's a physical break between it and the elements above and below it. A <span> isn't block-level; instead, it's inline, so you can apply it to, for instance, a single phrase within a sentence.
We're not saying that you need to junk everything you've ever learned about HTMLfar from it! But add these two tags to your toolkit of solutions, and you'll be surprised how often you use them.
Classes and ids