function bannerSwitcher() {
	var pos;
  var num = Math.floor(Math.random()*4);
	num = num + 1;
	switch(num) {
	  case 1:
		  pos = "0px";
			break;
		case 2:
		  pos = "-280px";
			break;
		case 3:
		  pos = "-560px";
			break;
		case 4:
		  pos = "-840px";
			break;
		default:
		  pos = "0px";
	};
	$('#banner').css('background-position','10px '+pos+'');
};