overflow scroll

HTML

<body>
    
    <div id="leftSide"> woop </div>
    <div id="rightSide"> woop </div>
    
</body>

CSS

#leftSide{
    width:50%;
    height:100%;
    background-color:#bada55;
    display:block;
    float:left;
    position:fixed;
}

#rightSide{
    width:50%;
    height:1000px;
    float:right;
    display:block;
    background-color:#666;
    overflow:scroll;
}