<div id="container" style="padding:50px; background-color:#c0c0c0; position:relative; width:200px; height:200px;">
<div id="div1" style="width:100%; height:100%; border:2px solid blue;">
<div id="content" style="border:1px solid red; position:absolute; left:0; top:0;">absolute element</div>
</div>
</div>