请将CSS代码复制到下面表单中:

#b { width:1200px; padding:0 12px; background:#FFF; position:relative } .l { width:844px; float:left; border-right:1px solid #DDD; padding-right:10px; position:relative } .m { width:670px; float:left; border-right:1px solid #DDD; padding-right:10px; position:relative } .r { width:336px; float:right; padding-bottom:200px } .topbg { height:30px; background:url(images/a.png) repeat -20px 0 }