seven.onclick=function () {

box.className="box";

}

.box{width: 100px;height:100px;border:5px solid black;float: left;margin-left:20px;margin-top: 20px;

clear:both;}

设置了个点击触发函数。但是这个box的盒子的css并没有改变。求解

全代码：*{margin: 0;padding:0;}

/*body{background-color: #5a5b5b}*/

.zhezhao

{

width:100%;

height:100%;

background-color:#000;

/*透明三部曲，一般都要写上/

;/*opacity:0.5;

-moz-opacity:0.5;

filter:alpha(opacity=50);*/

filter:alpha(opacity=50);

-moz-opacity:0.5;

opacity:0.5;

position:absolute;

left:0;

top:0;

display:none;

z-index:1000;

}

#box{width: 100px;height:100px;border:5px solid black;float: left;margin-left:20px;margin-top: 20px;

clear:both;}

.box{width: 100px;height:100px;border:5px solid black;float: left;margin-left:20px;margin-top: 20px;

clear:both;}

.box1{position: absolute;bottom:20px;right:20px;width:320px;height:300px;border:5px solid #5a5b5b;

padding:20px;display: none; z-index:1500;}

.option1 span{;border:1px solid black;display: inline;margin-left: 20px;padding: 5px;cursor: pointer;}

.option2{margin-top: 50px;}

.option2 span{border:1px solid black;display: inline;margin-left: 20px;padding: 5px; cursor: pointer;}

.option3{margin-top: 50px;}

.option3 span{border:1px solid black;display: inline;margin-left: 20px;padding: 5px; cursor: pointer}

.option4{margin-top: 50px;margin-left:100px;}

.option4 span{border:1px solid black;display: inline;margin-left: 20px;padding: 5px;text-align: center;cursor: pointer}

/* span在设置了inline后width属性失效了；*/

请为下面的的DIV设置样式：