<html> <style> .box { border: 2px solid green; padding: 2px; } .container { border: 2px solid blue; height: 100px; width: 100px; position: absolute; padding:10px; } .leftright { position:absolute; left:0px; right:0px; top:0px; height:100px; } .topbottom { width: 100px; position:absolute; top:0px; bottom:0px; left:0px; } </style> <body> <div class="container"> <div class="leftright box"></div> <div class="topbottom box"></div> <div style="width:100%; height:100%; background: gray;"></div> </div> </body>