Those are the core browsers WT is targeting?
I wish! But sadly no. We also have to consider IE7, Safari (pc and Mac) and Opera and not just their latest versions either. I wish we didn't but that's web life. It was only after some discussion that we were able to drop support fir IE6!
Any change must be tested in all these, at various screen sizes, and on all six standard themes.
Okay, that makes sense. See the linked article on quirks mode for some caveats regarding earlier IE and Opera compatibility—this patch may not be sufficient for those clients: I didn't figure out how to add a width: attribute for the inside of the person boxes.