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<div id="wrapper">
    <div id="main">
        <div id="content">#content</div>
    </div>
    <div id="left">#left</div>
    <div id="right">#right</div>
</div>

#wrapper {
    height: 500px;
    min-width: 600px;
}
#main {
    height: 500px;
    width: 100%;
    float: left;
}
#content {
    background-color: #eee;
    margin-right: 200px;
    margin-left: 150px;
    height: 500px;
}
#left {
    background-color: #000;
    float: left;
    margin-left: -100%;
    width: 150px;
    height: 500px;
    color:white;
}
#right {
    background-color: #000;
    float: left;
    margin-left: -200px;
    width: 200px;
    height: 500px;
    color:white;
}