body {
		background-color: #F2F2F2;
	}
	
#principal {
	    position: absolute;
        left: 50%;
        top: 50%;
        width:  850px;
        height: 521px;
        margin-top: -260px;
        margin-left: -425px;
 
        overflow: auto;
        z-index: -1;

}