一个div容器内包含横排的多个div，如何让他们整体居中？除了padding和margin

[aeoluszzf]

代码如下
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<style type="text/css">
.main{width: 400px; height: 200px; background: #999;}
.dv{width: 100px; height: 100px; background: #999; float: left;}
</style>
<div class="main">
<div class="dv">dv1</div>
<div class="dv">dv2</div>
<div class="dv">dv3</div>
</div>

[muxrwc]

<style type="text/css">
.main{width: 400px; height: 200px; background: #999; text-align:center;}
.dv{width: 100px; height: 100px; background: #999; float: left; text-align:left;}
.center {
width:300px;
margin:auto;
}
</style>
<div class="main">
<div class="center">
<div class="dv">dv1</div>
<div class="dv">dv2</div>
<div class="dv">dv3</div>
</div>
</div>