#back-top { position: fixed; bottom: 30px; margin-left: -150px; }
#back-top a { width: 50px; display: block; text-align: center; font: 11px/100% Arial, Helvetica, sans-serif; text-transform: uppercase; text-decoration: none; color: #666; /* background color transition */
-webkit-transition: 1s; -moz-transition: 1s; transition: 1s; }
#back-top a:hover { color: #000; }
/* arrow icon (span tag) */
#back-top span { width: 40px; height: 40px; display: block; margin-bottom: 7px; background: #ddd url(../images/up-arrow.png) no-repeat center center; /* rounded corners */
-webkit-border-radius: 5px; -moz-border-radius: 5px; border-radius: 5px; /* background color transition */
-webkit-transition: 1s; -moz-transition: 1s; transition: 1s; position: fixed; right: 25px; bottom: 25px; }
#back-top a:hover span { background-color: #333; }