一个CSS图片显示的有关问题，一直卡在这了

body{background:url(../images/bg.jpg) center top no-repeat; background-color:#eff3f6;}
.x_key{background:url(images/key.jpg) 0 2px no-repeat; width:8px; height:13px; float:right; overflow:hidden;_margin-top:-1px;}
.ms_head{margin:auto auto 45px; width:960px;  color:#ffffff;height:70px;}
.ms_head .nav_2{background:url(images/app_merge_20120208.png)  no-repeat; width:162px; height:28px; float:left; margin-left:30px; font-size:15px; line-height:28px;margin-top: 10px;}
.ms_head .nav_m9{background-position: 0 0;}
.nav_m9 a{color:#7ccbf7  !important;text-decoration: none !important;}
.ms_head .nav_m8{background-position: 0 -33px;}
.nav_m8 a{padding-left:10px;color:#7ccbf7 !important;}
.ms_head .x_top{padding-top:7px; line-height:14px; width:70%; overflow:hidden;color:#FFF !important;float: right;}
.ms_head .x_top a:visited{color:#FFF;}
.x_top a:link{color:#FFF;}
.ms_head .x_bottom{float:left; line-height:40px;height:40px;_height:90px; width:840px;;postion:relative;left:0;top:0;}
.ms_head .op_nav{float:left;  margin-left:30px;position:relative;width:410px;}
.op_nav li{float:left; line-height:50px; padding:0 7px;}
.op_nav li a{color:#fff !important; font-size:16px;text-decoration:none;}
.op_nav li a:hover{color:#d4efff !important;text-decoration:none;}
.op_nav .x_sep{height:12px; border-left:1px solid #ABDCF6; font-size:0px; width:0px; float:left; margin-top:20px; overflow:hidden;}
.op_nav .floatClass{background:url(images/nav_1.jpg)  5px 5px no-repeat;padding-right:15px;}
.x_bottom .x_appName{float:left; font-size:14px;}
.x_bottom .x_search{background:url(images/app_merge_20120208.png) -164px 0px no-repeat; width:179px; height:28px; float:right; overflow:hidden; margin-top:12px;}
.x_bottom .x_search input{border:medium none; margin:7px 0 4px 10px; height:17px;line-height:17px;width:126px; float:left;color:#A1C8DB;}
.x_bottom .x_search a{float:left; width:40px; overflow:hidden; height:28px;}
.x_bottom  a:hover {text-decoration:none;}
a.app_logoPaPa:hover{text-decoration:none;}
.app_logo{background: url("images/app_logo.jpg") no-repeat scroll 0 0 transparent;background: url("images/app_logo.jpg") no-repeat scroll 0 0 transparent;color: #FFFFFF;cursor: pointer;float: left;font-size: 18px;height: 20px;margin-top: 20px;padding-top: 22px;text-decoration: none !important;width: 117px;color: #FFFFFF;cursor: pointer;float: left;font-size: 18px;height: 20px;margin-top: 20px;padding-top: 22px;text-decoration: none !important;width: 117px;}
.x_top .x_link{float:right; overflow:hidden; padding:0 5px;}
.x_sep{border-left:1px solid #ABDCF6; float:right; font-size:0px; width:0px; height:10px; margin-top:3px;_margin-top:1px; overflow:hidden;}
.op_nav .bord_mid{float:left;width:100%;background:none repeat white;}
.op_nav .current {background:transparent url(images/app_index.png) no-repeat scroll 3px 40px;}