Layout 3 Colunas CSS / HTML

HTML <div id="container"> <div id="header"> dfgfdgdgf </div> <div id="navigation"> dasdasdas </div> <div id="content-container1"> <div id="content-container2"> <%--<div id="section-navigation"> sdfsdfs </div> --%> <div id="content"> <form id="form1" runat="server"> <div> <asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server"> </asp:ContentPlaceHolder> </div> </form> </div> <div id="aside"> dasdasd </div> <div id="footer"> Copyright © Site name, 20XX </div> </div> </div> </div> CSS #container { margin: 0 auto; width: 900px; padding:0px; background: #fff; } #header { background: #ccc; padding: 20px; } #navigation { float: left; width: 100%; background: #333; } #content-container1 { background-color: #899; float: left; width: 100%; } #content-container2 { background-color: #009; float: left; width: 100%; } #section-navigation { background-color: #366; float: left; width: 16%; padding: 20px 0; margin: 0 2%; display: inline; } #content { background-color: #363; float: left; width: 600px; padding: 20px 0; margin: 0 0 0 2%; } #aside { background-color: #383; float: right; width: 250px; padding: 20px 0; margin: 0 2% 0 0; display: inline; } #footer { background-color: #983; clear: both; text-align: right; padding: 20px; height: 1%; }