HTML

Overlapping Div

<div id="container">
    <div id="navi">a</div>
    <div id="infoi"><img src="info_icon2.png" height="20" width="32"/>b</div>
</div>

#container {
    width: 100px;
    height: 100px;
    position: relative;
}

#navi, 
#infoi {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
}

#infoi {
    z-index: 10;
}