SOURCE

<div class="container"> 
　　<div class="main">
    　　<div class="content">main</div> 
    </div>
　　<div class="left">left</div> 
　　<div class="right">right</div> 
</div>

.left, .main, .right {
        float: left;
        min-height: 130px;
        text-align: center;
    }
    .left {
        margin-left: -100%;
        background: green;
        width: 200px;
    }

    .right {
        margin-left: -300px;
        background-color: red;
        width: 300px;
    }
    .main {
        background-color: blue;
        width: 100%;
    }
    .content{
        margin: 0 300px 0 200px;
    }