.back-to-top { 
 position: fixed;
 z-index:1004;
 bottom:0px;
 right:0px;
 width: 130px; 
 height: 34px; 
 background: url(../../images/top1.png) no-repeat; 
}

.back-to-top:hover { 
 position: fixed;
 bottom:0px;
 right:0px;
 width: 130px; 
 height: 34px; 
 background: url(../../images/top2.png) no-repeat; 
}