.left{
       background-color:#cccccc;
       border:2px solid #333333;
       width:200px;
       height:100px;
}
.leftfloat{
       background-color:#cccccc;
       border:2px solid #333333;
       width:200px;
       height:100px;
       float:left;
}
.right{
       background-color:#cccccc;
       border:2px solid #333333;
       height:100px;
}

<div class="left">div left float:none</div>
<div class="right">div right [www.mintao.net]</div>
<div class="leftfloat">div left float:left</div>
<div class="right">div right [www.mintao.net]</div>
<span class="left">span left float:none</span>
<span class="right">span right</span>