<div id="main" class="clear">
<div id="left">
</div>
<div id="right">
</div>
</div>
<div id="other">
</div>
/*-----------------------------------------------*/
#main{
backgroud-color:#aaa;
padding:10px;
}
#left{
background-color:#bbb;
padding:5px;
border:1px solid red;
100px;
height:100px;
float:left;
}
#right{
background-color:#ccc;
padding:5px;
border:1px solid red;
100px;
height:100px;
float:left;
border:1px solid red;
float:right;
}
.clear:after{
content:".";
height:0;
visibility:hidden;
display:both;
clear:both;
}