<style type="text/css">
background-color: #000;
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#bbb', endColorstr='#000');
background-image: -webkit-gradient(linear, left top, left bottom, from(#bbb), to(#000));
background-image: -webkit-linear-gradient(top, #bbb, #000);
background-image: -moz-linear-gradient(top, #bbb, #000);
background-image: -ms-linear-gradient(top, #bbb, #000);
background-image: -o-linear-gradient(top, #bbb, #000);
background-image: linear-gradient(top, #bbb, #000);
</style>

http://www.apphp.com/index.php?snippet=css-cross-browser-gradient

The following code will display a cross-browser CSS-gradients. Th add the right selector you can use rgba() for transparency.

Cross-Browser Gradient in CSS3

CSS3

CSS