Prueba.css

body {
	margin: 0;
}

header.main{

	background:url('assets/images/hero.jpg')no-repeat;
	background-size: cover;
	min-height: 400px;
}

header.main nav ul.navegador{
	float: right;
	margin-top: 10px;
	padding-top: 15px;
}    

header.main nav ul.navegador li{
	display: inline;
	margin: 0 10px;
	clear: both;
}  




/* XS size */
 @media screen and (max-width: 767px) {
 	
 }
/* SM size */
  @media screen and (max-width: 992px){
 	
 }
/* MD size */
  @media screen and (max-width: 1200px) {
 	
 }
/* LG size */
 @media screen and (min-width: 1200px) {
 	
 }