[Jura]

CSS3 is the more modern goodies people can add to sites for look and navigation control. CSS is basically what makes sites look the way they do except for graphics. Because of the advancements in CSS, older web browsers that people don't update can't view sites as well.

So some smart person made a way for Internet Explorer versions 6, 7, and 8 to view many parts of CSS3 correctly.
http://css3pie.com/
If you're stuck with IE anywhere or can't upgrade, this could do a lot.