var duration = 2000;
var width = 804;
var sliderbox;
var current = 0;
var number;
function initSliderTabs()
{
	if(sliderbox = document.getElementById("gallery").getElementsByTagName("ul").item(0))
	{
		number = Math.ceil($$('#gallery ul li').length/4);

		sliderbox.fx = new Fx.Morph(sliderbox, {duration: 700});
		
		/* next */
		$('btn-next').addEvent('click', function()
		{
			sliderbox.fx.cancel();
			if(++current>=number)
				current=0;
		
			sliderbox.fx.start({'left': -current*width});
		});
		
		/* prev */
		$('btn-prev').addEvent('click', function()
		{
			sliderbox.fx.cancel();
			if(--current<0)
				current=number-1;

			sliderbox.fx.start({'left': -current*width});
		});
	}
}

if (window.addEventListener)
	window.addEventListener("load", initSliderTabs, false);
else if (window.attachEvent)
	window.attachEvent("onload", initSliderTabs);