IE7 and FFox seem to render textboxes very slightly differently by default.
This seems to be fixed by setting their border-style and border-width css properties.
The odd thing is, it seems that out of all the options vstudios intellisense gives me, none of them match?
The closest I've found is
border-width:1px;
border-style:inset;
Edit: Trying to set the style for a textbox, they all appear to render differently in various browsers.