#back-top {
position: fixed;
bottom: 20px;
right:20px;
z-index: 2000;

}
#back-top span {
width: 46px;
height: 36px;
display: block;
background: url("images/backtotop.png") no-repeat;
}
#back-top span:hover {
    background: url("images/backtotophoover.png") no-repeat;
    background-repeat: no-repeat;
    display: block;
    height: 36px;
    width: 46px;
}

#span4 {
    width: 370px;
background: #9ac2e0;
padding-top: 20px;
}