#centro #background {
	height: 500px;
	background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}
#centro #background .overlay {
  background-color: rgba(0, 0, 0, .4);
}

#centro  #formulario_resultados{
  top: 310px;
  position: relative;  
	z-index: 10;
	width: 75%;
	margin-left: auto;
	margin-right: auto;
}