That’s right I can admit I don’t know everything there is to know about HTML.
That doesn’t stop me from being a little ashamed to admit that I just read about 5 HTML elements I hadn’t used (or heard of) before on the SEOmoz Blog.
My favorites? <acronym> & <optgroup> - I have to go find a use for those right now!!

Thanks for posting this - it was very timely. The optgroup tag is going to be a perfect solution for something I’m working on here at work.
Dave
Glad to help!
acronym tag is poorly supported by browsers. Most ignore it…
http://www.devguru.com/technologies/html/6166.asp
But yes, OPTGROUP is very handy..
I have to say, I’d never heard of COLGROUP before. Now that DOES look useful….
http://www.devguru.com/technologies/html/6236.asp
You know, I think I’ve seen that used - but it never clicked how handy it could be - I’m going to have to go out and buy a new HTML book (mine is 9 years old) and see what fun things I’m missing.