XML

And I've read quite a few. At least the authors of "HTML for dummies" or whatever don't imagine that they are genuises setting the world on fire.

I'm really tired of e-business people coming to me with comments like "I can't see why we can't do ..." and other comments which reflect the absolute lack of technical interest e-business people show for what should be their profession.

Especially if you're in the IT field or seeking to break into it (lots of interview fodder here). Most books start with the differences between XML and HTML, how to create a valid XML document, intro the DTD, etc.