window.addEvent('domready', function() {

	$$('.rollover').each(function(img) {
	    var src = img.getProperty('src');
	    var extension = src.substring(src.lastIndexOf('.'),src.length);
	    img.addEvent('mouseenter', function() { img.setProperty('src',src.replace(extension,'_' + extension)); });
	    img.addEvent('mouseleave', function() { img.setProperty('src',src); });
	});

});