Compatibility
Lately, there has been a lot of discussion about compatibility. FrontPage 2003 has made leaps and bounds in this arena with a new browser compatibility wizard/tester, but I am still of the firm belief that you should code to 1 generation below the current technology, if you're going to do it at all. Personally, I'd rather give people another reason to upgrade than continue the status quo, but I dunno.
At any rate, I found a graphic that pretty much sums it up. I have posted it here for your viewing pleasure:
Hope you like ;)