$(function(){
	var linkHeight = $("#header_left ul li").height();
	$("#header_left ul li a").each(function(){
		var linkWidth = $(this).width();
		var txt = $(this).text();
		var id = $(this).attr("id");
		$(this).prepend('<span class="ov">' + txt + '</span>');
		$(this).find("span.ov").css({
			width:(linkWidth),
			height:'0',
			display:'block',
			position:'absolute',
			cursor:'pointer',
			"font-size":"0",
			backgroundImage:'url(img/btn'+id+'_on.jpg)'
		});
	});
	$("#header_left ul li a").hover(function(){
		$(this).children('span.ov').stop().animate({height:(linkHeight)},300);
	}, function(){
		$(this).children('span.ov').stop().animate({height:'0'},300);
	});
});