//ボタンのロールオーバー画像切り替え用スクリプト
rollovers=function(off, on) {
	img=document.getElementsByTagName("img");
	p=[];
	off_reg=new RegExp(off+"(\.[a-z]+$)","i");
	on_reg=new RegExp(on+"(\.[a-z]+$)","i");
	for(var x=0,i;i=img[x];x++) {
		if(i.src.match(off_reg)) {
			p[x]=new Image();
			p[x].src=i.src.replace(off_reg,on+"$1");
			i.onmouseover=function() {
				this.src=this.src.replace(off_reg,on+"$1");
			};
			i.onmouseout=function() {
				this.src=this.src.replace(on_reg,off+"$1");
			};
		};
	};
};

window.onload = function() {
  rollovers("_n", "_o");
};