var RollOver = Class.create();

RollOver.prototype = {

initialize: function(option) {

var props = {

hclass : "btn",

suffix : "-on"

};

if(option) for(var key in option) props[key] = option[key];

$$('img.'+props.hclass,'input.'+props.hclass).each(

function(el){

var osrc = el.getAttribute('src');

if (!osrc) return;

var hsrc = osrc.replace(/(\.gif|\.jpg)/,props.suffix+'$1');

(new Image()).src = hsrc;

el.observe("mouseover",function(){

el.setAttribute('src', hsrc);

}).observe("mouseout",function(){

el.setAttribute('src', osrc);

});

}

);

}

}//prototype

Event.observe(window,'load',function(){new RollOver();});