dl.back{ height: 120px; float: left; position: relative; width: 920px;}
dl.back dd.back_no_btn{float: left; margin-top: 50px; top: 0px; left: 280px; position: absolute;}
dl.back dd.back_no_btn a{width: 400px; text-align: center; color: white; padding: 10px; background-color: #7f7f7f; float: right;}
dl.back dd.back_no_btn a:hover{text-decoration: none;}