body { background-color: white; margin: 0; }
#header { width: 800px; }
#topbanner { width: 765px; margin-top: 20px; margin-right: auto; margin-left: auto; }
#pageflip { width: 800px; height: 600px; margin-right: auto; margin-left: auto; }
#contenido { width: 800px; margin-right: auto; margin-left: auto; }