#roll_top, #fall, #ct
{
    position: relative;
    cursor: pointer;
    height: 41px;
    width: 40px;
}
#roll_top
{
    background: url(../Img/top.gif) no-repeat;
}
#fall
{
    background: url(../Img/top.gif) no-repeat 0 -80px;
}
#ct
{
    background: url(../Img/top.gif) no-repeat 0 -40px;
}
#roll
{
    display: block;
    width: 15px;
    margin-right: -500px;
    position: fixed;
    right: 44%;
    top: 80%;
    _margin-right: -505px;
    _position: absolute;
    _margin-top: 300px;
    _top: expression(eval(document.documentElement.scrollTop));
}