CSS3 Fade

<style>
#fade{
opacity:1;
-moz-transition: opacity 1s linear; /* Firefox */
-webkit-transition: opacity 1s linear; /* Chrom, Safari */
-o-transition: opacity 1s linear; /* Opera */
background-color:#666;
color:#fff;
padding:5px;
}

#fade:hover{
opacity:0;
}
</style>
<div id=fade>Place mouse on me!</div>