老师帮我看看问题出现在哪里，我main部分动不了,顺便帮我看看我的遮罩层为什么用不了

*{

margin: 0;

padding: 0;

overflow: hidden;

}

.big{

width: 100%;

height: 1200px;

}

.header{

background-color:#00BFFF;

width: 100%;

height: 100px;

cursor:pointer;

position: fixed;

top:0;

left: 50%;

margin-left: -50%;

margin-top: 0px;

/**/

}

.header .tu1{padding:20px 30px; height: 48px;}

.header .list { float: right;padding-top: 30PX;}

.header .list li:hover{background-color: #000;}

.header .list ul{height:}

.header .list li{

display: inline;

list-style-type: none;

padding: 20PX;

color:#FFF;

}

.header .list .one{text-decoration:none;}

 .main{

         width: 100%;

min-width: 800px;

height: 1200PX;

font-size: 0;

margin-top: 100px;

font-size: 0;

}

.main .main-top{width: 100%; height: 800px;}

.main .main-top .tu2{width: 100%; height: 800px;}

.main .toplayer{

position: absolute;

top:100px;

left: 0;

width: 100%;

height: 800px;

background-color:#000;

opacity:0.5;

}