Create a "wrapper" div to hold all your content and apply its width property through CSS, then give it a margin:auto attribute
<style type="text/css"> #wrapper {width: 760px;margin:auto} #content{background-color:red} </style> </head> <body> <form id="form1" runat="server"> <div id="wrapper"> <div id="content"> content </div> </div> </form> </body>