#billboard
{    
	width:100%;
	margin-top:20px;
	text-align:center;
}

#billboard_ad
{
	width:30%;
	height:auto;
	/*
	width: 250px;
	height: 70px;
	*/
	border-radius:5px;
	border: 1px solid #aaa;	
	/*margin-left:5px;*/
	margin-bottom: 5px;
	
}

@media only screen and (max-device-width: 480px)
{
	#billboard_ad
	{ 
		width:47%;
		height:auto;
		border-radius:5px;
		border: 1px solid #aaa;	
		margin-bottom: 5px;
	}
}