body {
      
      margin:0% 0% 0% 0%;
      width: 100%;
   
background: url(../img/bg-latastel.jpg) no-repeat #000;
-webkit-background-size: contain;
-moz-background-size: contain;
-o-background-size: contain;
background-size: cover;    }
      
.principal {
margin: 0 auto;
width: 100%;

        }
        
        


              
.logo {
margin: 40% auto;
width: 50%;

        }	
        
.boton {
margin: -40% auto;
width: 30%;

        }