html, body {margin: 0; padding: 0; background: #b00e0e;}
#contenedor {width:780px; height:560px; margin:10px auto; position:relative;}
#contenido {width: 780px; height: 560px; position: absolute; top: 10px; left: 10px; padding: 10px 20px 10px 10px; overflow: auto;}
/* invisible para IE 5 */
#contenedor {position:absolute; margin:-280px 0 0 -390px; left:50%; top:50%;}