/*
    Thanks inputlog ? prototype.jsとロールオーバー
    http://blog.kyosuke.jp/item/21
*/
overImgClassName = 'rollover';
overImgPostfix = '_on';
Event.observe(window, 'load', RN_setMouseOverImages, false);
function RN_setMouseOverImages() {
    var btns = $A(document.getElementsByClassName(overImgClassName));
    btns.each(function (node){
        node.imgsrc = node.src;
        node.imgsrc_over = node.src.replace('.gif', overImgPostfix+'.gif').replace('.jpg', overImgPostfix+'.jpg');
        node.onmouseover = function() { this.src = this.imgsrc_over; };
        node.onmouseout = function() { this.src = this.imgsrc; };
    });
}