#site-box {
          width : 650px;
}

  div {  
       zoom: 1;/*for IE 5.5-7*/  
    }  
   div:after {/*for modern browser*/  
        content: ".";  
        clear: both;  
        display: block;  
        line-height: 0;  
        height: 0;  
       visibility: hidden;  
   }