$(document).ready(function () {
		$('#menu ul li').hover(
			function (e) {
				// Over...
				var image = $(this).find('img')[0];
				var srcinfo = image.src.match(/(.*\/)([a-z]+)\.gif/);
				image.src = srcinfo[1]+srcinfo[2]+'_on.gif';
			},
			function (e) {
				// Out...
				var image = $(this).find('img')[0];
				var srcinfo = image.src.match(/(.*\/)([a-z]+)_on\.gif/);
				if (image && srcinfo) {
					// If, in IE6 at least, the images are not loaded but the mouseover event occurs, srcinfo will be
					// null, and the next line will throw an error. So, the "if" skips it if the image isn't ready.
					image.src = srcinfo[1]+srcinfo[2]+'.gif';
				}
			}			
		);
	}
);