PIE makes Internet Explorer 6-8 capable of rendering several of the most useful CSS3 decoration features.
CSS3 promises to do away with all that! But as we all know, due to Internet Explorer’s lack of support for any of these features, we must be patient and refrain from using them, and make do with the same old tedious techniques for the foreseeable future.
Or must we?
PIE stands for Progressive Internet Explorer. It is an IE attached behavior which, when applied to an element, allows IE to recognize and display a number of CSS3 properties.
Learn more at http://css3pie.com/