#fondo_alerta{
	width: 100%;
	height: 100%;
	position: fixed;
	top: 0px;
	background: rgba(0,0,0,0.5);
	z-index: 100; 
}
#mensaje_alerta{
	position: relative;
	z-index: 101;
	background: white;
	width: 50%;
	min-height: 25px;
	margin-left: 25%;
	text-align: center;
	margin-top: 5%;
}#cuerpo_alerta{
	width: 100%;
	text-align: center;
	position: relative;
	padding-bottom: 10px;
	padding-top: 10px;
}
#cerrar_alerta{
	width: 100%;
	position: relative;
	bottom: 0px;
	left: 0px;
}