<style type="text/css">

​

body { margin: 0; padding: 0}

​

#container {

    position: absolute;

    top: 30px; left: 50px;

    bottom: 30px; right: 50px;

    border: 1px solid #ccc

}

  .item{height:100%}

​

  .item.first { background: red;width: 33%;float:left; margin-right:15px}

  .item.middle { background: green; margin: 0 15px;overflow:hidden;}

  .item.last { background: blue;width: 33%;float:right;margin-left:15px}

​

</style>

​

<div id="container">

    <div class="item first"></div>

        <div class="item last"></div>

    <div class="item middle"></div>

</div>