Background Color Hover Fade Effect CSS
Since this is a cosmetic effect, it shouldn't be too vital that this fires. Given that, you might want to look at CSS 3 transformations.
a { color: #000; transition: background 0.5s linear;}a:hover { background-color: #d1d1d1; color: #fff;}<a href="http://example.com">Hover me</a>
The CSS3 Transition effect would work for what you are looking for. You can find more info on how to use it here: http://www.css3.info/preview/css3-transitions/
You cannot animate the background color until you use a plug-in. The plug in is designed by the same guy who created jQuery though: http://plugins.jquery.com/project/color
He just didn't include it because it would have made the js file bigger.
Note: you can change the opacity though.