<body style="width:100%;height:100%;margin:0;padding:0;"> <div id="004" style="float:left;position:absolute;width:100%;height:100px;background:green;bottom:0px;margin:0;padding:0;">aaa </div> <div id="001" style="float:left;position:absolute;width:100%;height:100%;bottom:100px;margin:0;padding:0;"> <div id="002" style="float:left;width:200px;background-color:blue;height:100%;margin:0;padding:0;">bbb</div> <div id="003" style="background-color:red;height:100%;margin-left:200px;margin:0;padding:0;">ccc</div> </div> </body> HTML: DIV001 AND DIV004 are parent div, DIV002 AND DIV003 are child div of DIV001. I want body: height 100%,width 100%; DIV004 fix on the bottom, height 200px,width 100%; DIV001 width 100%, heght 100%-200px, DIV002 width 200px,height 100% of DIV001, DIV003 width 100%-200px of DIV001,height 100% of DIV001. how to calculate the div width and height? Thanks.