这样对的么
*{margin:0; padding:0;}
#wrap{width:970px;margin:0 auto;}
#mainbody{margin-top:15px;position:relative;}
#left{width:110px;float:left;border:1px solid #999; }
#mid{width:650px;border:1px solid #999;float:left;margin-left:13px;}
#right{position:absolute;border:1px solid #999;margin-left:790px;}
</style>