>I strongly disagree with this advice

No that's not what I meant.

IE is used by more people than firefox, fact. Don't they have 90% of the market share ? Anyway you need to make sure it's displaying ok in IE at the very least. Seems the OP is neglecting this fact. In the code he posted the mouseovers don't work for IE. Well, at least that's what I found when I tested it.

I'm not saying write your code in a **** poor way such that it only works in IE. No far from it.

Like you said writing good standard code to display correctly across the most popular browsers is paramount.