// pre-cache off images
	var offArray = new Array()
		offArray["previous"] = new Image();
		offArray["next"] = new Image();
		
	// set off image paths
	offArray["previous"].src = "../images/prevarrow_off.gif";
	offArray["next"].src = "../images/nextarrow_off.gif";
		
	// pre-cache roll images	
	var rollArray = new Array()
		rollArray["previous"] = new Image();
		rollArray["next"] = new Image();

	// set roll image paths
	rollArray["previous"].src = "../images/prevarrow_on.gif";
	rollArray["next"].src = "../images/nextarrow_on.gif";

	function imgRoll(imgName) {
		document.images[imgName].src = rollArray[imgName].src;
	}

	function imgOff(imgName) {
		document.images[imgName].src = offArray[imgName].src;
	}