.project_bg {
     background-image: url('../images/project_2.png');
     width:1200px;
     background-size:100% 100%;
     min-height:808px;
     background-position:center
}
.top_img{text-align:center;margin-top:60px;}
.zs_list,.zs_list_last{width:840px;margin:0 auto;margin-top:20px;clear:both;height:200px}
/*.zs_list:after,.zs_list_last::after{content:url(../images/zs_right.png);position:absolute;margin-top:80px;}*/
.zs_list li{width:200px;float:left;text-align:center}
.zs_list_last li{width:400px;float:left;text-align:center}