<style>

body { margin: 0; padding: 0}

​

#container {

    position: absolute;

    top: 30px; left: 50px;

    bottom: 30px; right: 50px;

    border: 0px solid #ccc

}

​

#container > div {

    width: 33.33%;

    height: 100%;

    float: left;

}

#container div div {

    height:100%;

}

#container div div.a {

    background: red; margin-right: 20px; 

    -webkit-border-radius: 22px;

    -moz-border-radius: 22px;

    border-radius: 22px;

}

#container div div.b {

    background: green; margin:0 20px;

  -webkit-border-radius: 22px;

    -moz-border-radius: 22px;

    border-radius: 22px;

}

#container div div.c {

    background: blue; margin-left: 20px

      -webkit-border-radius: 22px;

    -moz-border-radius: 22px;

    border-radius: 22px;

}

</style>

​

<div id="container">

        <div><div class="a">First</div></div>

        <div><div class="b">Second</div></div>

        <div><div class="c">Third</div></div>

</div>