#roll_top, #fall, #ct
{
    position: relative;
    cursor: pointer;
    width: 26px;
    padding: 5px;
    text-align: center;
}
#roll_top
{
    background: #00b0d6;
}
#roll_top:before
{
    content: '返回顶部';
    font-size: 14px;
    color: #fff;
}
#fall
{
    background: url(/Skins/Default/Img/top.gif) no-repeat 0 -80px;
}
#ct
{
    background: url(/Skins/Default/Img/top.gif) no-repeat 0 -40px;
}
#roll
{
    display: block;
    width: 15px;
    width: 15px;
    margin-right: -500px;
    position: fixed;
    right: 50%;
    bottom: 20%;
    _margin-right: -500px;
    _position: absolute;
    _margin-bottom: 300px;
    _top: expression(eval(document.documentElement.scrollTop));
}