i have the following selector in my css:
a:active { position: relative; top: 1px; }
So every link has this little button-effect when it\'s
i think you should "reset" the top decleration
a#back-to-top:active { position:fixed; bottom:20px; top: auto; }
also, use !important only if for some reason the a#back-to-top:active style declartion comes before a:active one.