css背景图片拉伸满屏

body{margin:0;font-family:'Microsoft YaHei';background:url('../images/bg.png') ;}
.box{width:100%;margin:0 auto;}
.top{height:179px;background:url('../images/top.jpg');position:relative;background-size:100%;}
.title{padding-left:60px;color:#000;font-size:40px;letter-spacing:5px;line-height:160px;}
.nav{position:absolute;right:0;bottom:6px;}
.nav a{color:#000;padding:6px 12px;background:#9cb945;text-decoration:none;}
.nav a:hover{color:#fff;}
.main{padding-bottom:10px;background:#fff;color:#333;}

.news-title{font-size:20px;text-align:center;padding:15px 0;width:70%;margin:0 auto;border-bottom:1px solid #999;font-weight:bold;}
.news-time{text-align:center;margin-top:10px;}
.news-content{width:70%;margin:20px auto;}

.news-edit{width:100%;margin:0 auto;padding-top:20px;}
.news-edit th{width:80px;font-weight:normal;vertical-align:top;padding-bottom:10px;}
.news-edit td{padding-bottom:10px;}
.news-edit input[type=text]{width:60%;border:1px solid #A2BBEA;padding:4px;border-radius:5px;font-family:'simsun';}
.news-edit input[type=text]:hover{background:#eeeeff;}
.news-edit textarea{width:80%;height:150px;border:1px solid #A2BBEA;padding:4px;border-radius:5px;font-family:'simsun';}
.news-edit textarea:hover{background:#eeeeff;}
.news-edit input[type=submit]{padding:5px 12px;cursor:pointer;}

.news-list{width:100%;border-collapse:collapse;margin-bottom:10px;}
.news-list th{background:#0088cc;color:#fff;padding-top:5px;padding-bottom:5px;border:2px solid #fff;}
.news-list td{border-bottom:2px dashed #ccc;padding:8px;}
.news-list-title{text-indent:20px;}
.news-list a{color:#116FCE;text-decoration:none;}
.news-list a:hover{text-decoration:underline;}
.center{text-align:center;}

.pagelist{text-align:center;padding-bottom:10px;}
.pagelist a{color:#116FCE;text-decoration:none;}
.pagelist a:hover{text-decoration:underline;}

.action{margin-bottom:15px;}