yui/yui3 — comment on commit e1d2c90eed2334936210d1e1c6c53a43934ed517
File: src/button/css/cssbutton.css line 7
By derek:

To provide consistent look/feel. Buttons have a larger text in IE6/7. So 100% size in everything else should actually be about 90% size in IE 6/7.