window.onload = initRollovers;

function initRollovers()
{
	var images = document.getElementsByTagName('img');
	for (var i = 0; i < images.length; i++)
	{
		var image = images[i];
		var rolloverURL = image.getAttribute('rollover');
		if (rolloverURL) addRollover(image, rolloverURL);
	}
	
	// add functionality for images used as submit buttons
	var submitImages = document.getElementsByTagName('input');
	for (var i = 0; i < submitImages.length; i++)
	{
		var submitImage = submitImages[i];
		var rolloverURL = submitImage.getAttribute('rollover');
		var type = submitImage.getAttribute('type');
		if (type == 'image') addRollover(submitImage, rolloverURL);
	}
}

function addRollover(img, rolloverURL)
{
	if (typeof img == 'string')// if img is string
	{
		var id = img;// it is an id, not an image
		img = null;// and we don't yet have an image
		
		// try looking the image up by id
		if (document.getElementById) img = document.getElementById(id);
		else if (document.all) img = document.all[id];
		
		// if not found by id try finding by name
		if (!img) img = document.images[id];
		
		// if no image found then fail silently
		if (!img) return;
	}
	
	// remember the original URL of the image
	var baseURL = img.src;
	
	// Preload the rollover image into the browser's cache
	(new Image()).src = rolloverURL;
	
	img.onmouseover = function(){img.src = rolloverURL;}
	img.onmouseout = function(){img.src = baseURL;}
}