.tong{width:100%;float:left;background-color:#eaeaea;z-index:999;position:fixed;top:0px;}
 .head{width:1000px;margin:0px auto;height:25px;font-size:13px;}

居然可以浮在上面跟着走

.head_tong{width:100%;height:98px;overflow:hidden;position:fixed;float:left;background:url('../images/2012sjgmr_bj.jpg') repeat-x;
 bottom:0;margin:0px auto;z-index:999;padding:0px;}
 .tong{width:960px;position:relative;margin:0px auto;}
 .tong img{width:960px;height:98px;}