var preloadedImages = new Array();

function preloadImages(locationFolder) {
    if(document.images) {
            var i, args = preloadImages.arguments; 
            for(i=1; i<args.length; i++) {
                preloadedImages[args[i]]     = new Image(); 
                preloadedImages[args[i]].src = locationFolder + args[i] + '.gif';
            }
    }
}


function rollOn(imageName) {
    if(document.images && preloadedImages[imageName + "_over"]) {
    	document.images[imageName].src = preloadedImages[imageName + "_over"].src;
    }
}


function rollOff(imageName) {
    if(document.images && preloadedImages[imageName + "_over"])
	document.images[imageName].src = preloadedImages[imageName + "_normal"].src;
}