function swap(element, event) {
	var image;
	image = element.src;
	var len = image.length;
	var us = image.indexOf('_');
	var fs = image.lastIndexOf('.');
	var ext = image.substr(fs);
	if(event.type == 'mouseover') {
		image = image.substr(0, fs) + '_hover' + ext;
	} else if(event.type == 'mouseout') {
		if(us >= 0) {
			image = image.substr(0, us) + ext;
		} else {
			image = image;
		}
	}
	element.src = image;

}