To set the divs’ position horizontally fixed but not vertically, use the following code :

HTML

<div id="container">
    <div id="manu"></div>
</div>

CSS

<style type="text/css">
#container {
 position:relative;
    width:700px;
 height:1000px;
    top:50px;
    left:50px;
 background-color:yellow;

}

#manu{
    position:fixed;
    width:100px;
    height:100px;
    background-color:blue;
    margin-top:20px;
    margin-left:400px;
}
</style>

Jquery

<script type="text/javascript">
$(window).scroll(function(event) {
   $("#manu").css("margin-left", 400-$(document).scrollLeft());
});
</script>

To see demo please click the link below :

http://jsfiddle.net/kL33K/