Basically speaking, FF3 and IE8 render it this way, which is what I want:
http://img4.imageshack.us/img4/3899/cornersfirefox.jpg
However, IE7 and IE8 render it like this:
http://img18.imageshack.us/img18/4526/cornersie.jpg
I use this solution for rounded corners without images:
http://www.editsite.net/blog/rounded_corners.html
And finally, here is my code and CSS (dynamically generated, so sorry for the lack of proper tabbing):
Thank you in advance!