#back-top {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 9999;
}
 
#back-top a {
    width: 88px;
    display: block;
    text-align: center;
    font: 11px/100% Arial, Helvetica, sans-serif;
    text-transform: uppercase;
    text-decoration: none;
    outline: none;
    color: #bbb;
 
    /* transition */
    -webkit-transition: 1s;
    -moz-transition: 1s;
    -o-transition: 1s;
    transition: 1s;
 
    filter: alpha(opacity=50);
    -moz-opacity: 0.5;
    opacity: 0.5;
}
#back-top a:hover {
    color: #000;
 
    filter: alpha(opacity=100);
    -moz-opacity: 1.0;
    opacity: 1.0;
}
 
/* arrow icon (span tag) */
#back-top span {
    width: 88px;
    height: 88px;
    display: block;
    margin-bottom: 7px;
    background: #ddd url(../img/backtop.png) no-repeat center center;
 
    /* rounded corners */
    -webkit-border-radius: 15px;
    -moz-border-radius: 15px;
    border-radius: 15px;
 
    /* transition */
    -webkit-transition: 1s;
    -moz-transition: 1s;
    -o-transition: 1s;
    transition: 1s;
}
#back-top a:hover span {
    background-color: #eee;
}