$(document).ready(
function()
{
	$("#topmenu img").hover(
	function()
	{
		url = $(this).attr('src');
		baseurl = url.substr(0, url.length - 4);
		url = baseurl + 'O.gif';
		$(this).attr('src', url);
	},
	function()
	{
		url = $(this).attr('src');
		baseurl = url.substr(0, url.length - 5);
		url = baseurl + '.gif';
		$(this).attr('src', url);
	}
	);
});