"SELECT" and CSS with BROWSER Compatible Issues

Just gone through an issue regarding adding some style sheets on the "OPTION" tag of the "SELECT" box... and come up with an browser compatible issue that IE do not support such type of work. However Firefox goes well.Lets have an example:If we want to highlight, change selected value fonts or make changes in the font-weight it will not effect in IE at all.Just have a look this code in Both browsers and have a look the difference :
This is bold text
This is normal text

This is also being under discussion from several analysis point of view that IE may have playing some contradictory part with OPTGROUP. Here i am also mentioning couple of discussion forum links where these issues came under observations. Hope some or none might help you in knowing these in near future.

Forum Discussion 1 - forums.devshed.com
Forum Discussion2 - forums.whirlpool.net.au