// Thanks to Kyosuke Nakamura

$(function() {
	var conf = {
		className : "imgover",
		postfix : "_o"
	};
	$('.'+conf.className).each(function() {
		this.originalSrc = this.src;
		// alert('original:'+this.originalSrc); //debug
		this.rolloverSrc = this.originalSrc.replace(/(\.gif|\.jpg|\.png)/, conf.postfix+"$1");
		// alert('rollover:'+this.rolloverSrc); //debug
		preloadImage(this.rolloverSrc);
	}).hover(function() {
		this.src = this.rolloverSrc;
	},function() {
		this.src = this.originalSrc;
	})
});

// preload
preloadedImages = [];
function preloadImage(url) {
	var p = preloadedImages;
	var l = p.length;
	p[l] = new Image();
	p[l].src = url;
	// alert('preloaded' + url); //debug
}