$(function() {
	$(".btn")
		.mouseover(function () {
			this.src = this.src.replace(/^(.+)(.png)$/, "$1_over$2");
		})
		.mouseout(function () {
			this.src = this.src.replace(/^(.+)_over(.png)$/, "$1$2");
		})
		.each(function () {
			this.preloaded = new Image;
			this.preloaded.src = this.src.replace(/^(.+)(.png)$/, "$1_over$2");
	});
});