div#left {position:absolute;top:75px;left:0px;width:10%;height:100%;}
div#leftArr {position:fixed;top:50%;left:5%;visibility:hidden;}
div#right {position:absolute;top:75px;right:0px;width:10%;height:100%;}
div#rightArr {position:fixed;top:50%;right:5%;visibility:hidden;}