PIE stands for “Progressive Internet Explorer”, and is capable to add support for the most useful, cool CSS3 features, to the old and grumpy internet explorer (6, 7 and 8), and make your life easier.

Look and this page ( http://www.antimath.info/demos/csspie/ ) in internet explorer, … border-radius, box-shadow, background gradient, …good bye images and useless markup, hello PIE.

.element {
   width: 250px;
   height: 150px;
   line-height: 150px;
   font-style: italic;
   text-align: center;

    border: 1px solid #999;
    -webkit-border-radius: 10px;
    -moz-border-radius: 10px;
    border-radius: 10px;

    -webkit-box-shadow: #444 0 0 10px;
    -moz-box-shadow: #444 0 0 10px;
    box-shadow: #444 0 0 10px;

    background: #CCC; /*non-CSS3 browsers will use this*/
    background: -webkit-gradient(linear, 0 0, 0 100%, from(#BEE224) to(#E9F648)); /*old webkit*/
    background: -webkit-linear-gradient(#BEE224, #E9F648); /*new webkit*/
    background: -moz-linear-gradient(#BEE224, #E9F648); /*gecko*/
    background: -ms-linear-gradient(#BEE224, #E9F648); /*IE10 preview*/
    background: -o-linear-gradient(#BEE224, #E9F648); /*opera 11.10+*/
    background: linear-gradient(#BEE224, #E9F648); /*future CSS3 browsers*/
    -pie-background: linear-gradient(#BEE224, #E9F648); /*PIE*/

    behavior: url(pathTo/PIE.htc);
}

CSS3 PIE supports:

• border-radius
• box-shadow
• border-image
• multiple background images
• linear-gradient as background image

See more on css3pie.com