^It's a little more complicated than that. Using the center tag only will make it work in IE, but not FF.
I've found that if you surround your DIV like this with tables, it works in all broswers:
<center><table><div style="attributes here;"></div></table></center>
... don't ask me why, but it's the only way to get it compatible. Of course, that's an example for website coding. Since that last div is open, I'd assume only the first half of that coding is needed.