On my site, I'm using the JavaScript Tabifier to create tabs
In Firefox, the tabs have a top border (as desired).
In IE 6/7, the tabs do not have a top border, even though I have border-top defined for the appropriate CSS property (ul.tabbernav li a).
Any CSS ideas as to why Firefox has the top border but IE does not?
UPDATE
Per comment below, the page now w3c validates BUT I am still experiencing the CSS issue as originally outlined.
UPATE 2
Yes, I'm aware IE 6/7/8 does not support border-radius but I have removed that property and explicitly defined border-top and the border-top is still not displaying for IE 6/7.