body { 
  background: url('../startbilder/Sandkrausegrau.jpg') no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

.col_centered {
  display: block;
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

.preview_img {
	margin-top: 50px;
}

.image_big {
   display: none !important;
}

.margin_bottom {
	margin-bottom: 50px !important;
}


@media (min-width: 620px) { 
	
	.margin_left {
		margin-left: 50px !important;
	}
	
	.margin_top {
		margin-top: 0px !important;
	}
	
	.margin_bottom {
		margin-bottom: 70px !important;
	}
	
	.image_small {
	   display: none !important;
	}
	
	.image_big {
	   display: inline !important;
	}
}
	
	
@media (min-width: 767px) { 
	.row {
		margin-top: 50px;
	}
	
	.margin_left {
		margin-left: 50px !important;
	}
}