From 2007.igem.org

1. roll {

width: 695px;
height: 550px;
background: url() no-repeat;
margin: 10px auto; padding: 0;
position: relative;
border: 2px solid #999;

}

1. roll li {margin: 0; padding: 0; list-style: none; display: block; position: absolute;}

1. roll a {display: block; text-indent: -9999px; text-decoration: none;}

1. true {left: 175px; top: 235px; width: 700px; height: 25px;}
2. true a {height: 80px;}
3. true a:hover {background: url(https://static.igem.org/mediawiki/2007/c/c8/Agarose_gel_info.png) -0px -115px no-repeat;}

1. false {left: 175px; top: 125px; width: 500px; height: 75px;}
2. false a {height: 112px;}
3. false a:hover {background: url(https://static.igem.org/mediawiki/2007/c/c8/Agarose_gel_info.png) no-repeat;}

1. negative {left: 175px; top: 320px; width: 570px; height: 25px;}
2. negative a {height: 73px;}
3. negative a:hover {background: url(https://static.igem.org/mediawiki/2007/c/c8/Agarose_gel_info.png) -0px -200px no-repeat;}