$(document).ready ( function() {	
	$('#logo a img').addClass('roll'); // set roll over images
	
	var imgs = $(".roll");
	var parentimg = imgs.parent();
	imgs.each(function() { 
		var url = $(this).attr('src');
		var ftype = url.substring(url.lastIndexOf('.'), url.length);
		var fname = url.substring(0, url.lastIndexOf('.'));
		var output = fname + '-over' + ftype; 
			if(output) {
				$(this)
				.hover(function() {
					$(this).attr('src',	output);  
					  },
					function() {
					$(this).attr('src',	url);	
					});
			}
	});
});