function win_load(){
	
	var n_a=document.getElementById('index_nav').getElementsByTagName('a');
	var nav_over=function (){
		var img=this.getElementsByTagName('img')[0];
		if(img.src.search("_over.gif")==-1)img.src=img.src.replace('.gif','_over.gif');
	}
	var nav_out=function (){
		var img=this.getElementsByTagName('img')[0];
		if(img.src.search("_over.gif")!=-1)img.src=img.src.replace('_over.gif','.gif');
	}
	
	for(var i=0;i<n_a.length;i++){
		YAHOO.util.Event.on(n_a[i], 'mouseover', nav_over);
		YAHOO.util.Event.on(n_a[i], 'mouseout', nav_out);
	}
}

YAHOO.util.Event.addListener(window, 'load', function(){
													 win_load();
													  });