$.fn.naviStartAnimate = function() {
	this.each(function() {
		// check already starts
		var tm = $.data(this, "tmAnimate");
		if (typeof(tm)!='undefined' && tm > -1) {
			clearInterval(tm);
		}
		
		// start timer
		var $this = $(this);
		var sw = true;
		var tmAnimate = setInterval(function(){
			if (sw) {
				$this.stop().animate({
					opacity: .3
				}, 1000);
			} else {
				$this.stop().animate({
					opacity: 1
				}, 1000);
			}
			sw = !sw;
		}, 1000);
		
		$.data(this, "tmAnimate", tmAnimate);
	});
};

$.fn.naviStopAnimate = function() {
	this.each(function() {
		var tmAnimate = $.data(this, "tmAnimate");
		clearInterval(tmAnimate);
		$(this).css("opacity", 1);
		$.data(this, "tmAnimate", -1);
	});
};
