function show(elementId){
		document.getElementById(elementId).style.visibility = "visible";
	}
	function hide(elementId){
		document.getElementById(elementId).style.visibility = "hidden";
	}
	
	function slideInDivOne(){
		hide("two");
		hide("three");
		hide("four");
		show("one");
		slideIn("one");
	}
	function slideOutDivOne(){
		slideOut("one");
	}
	function slideInDivTwo(){
		hide("one");
		hide("three");
		hide("four");
		show("two");
		slideIn("two");
	}
	function slideOutDivTwo(){
		slideOut("two");
	}
	function slideInDivThree(){
		hide("one");
		hide("two");
		hide("four");
		show("three");
		slideIn("three");
	}
	function slideOutDivThree(){
		slideOut("three");
	}
	function slideInDivFour(){
		hide("one");
		hide("two");
		hide("three");
		show("four");
		slideIn("four");
	}
	function slideOutDivFour(){
		slideOut("four");
	}
	
	function slideIn(elementId){
		var slideInAttributes = {
			width: { from: 0, to: 400 },
			opacity: { from: 0, to: 1 }
		};
		slideInElement = new YAHOO.util.Anim(elementId, slideInAttributes);
		slideInElement.animate();
	}
	
	function slideOut(elementId){
		var slideOutAttributes = {
			width: { from: 400, to: 0 },
			opacity: { from: 1, to: 0 }
		};
		slideOutElement = new YAHOO.util.Anim(elementId, slideOutAttributes);
		slideOutElement.animate();
	}
	
	// register events 
	YAHOO.util.Event.on('divOneButton', 'click', function() {
		slideInDivOne();
	});
	
	YAHOO.util.Event.on('divOneCloseButton', 'click', function() {
		slideOutDivOne();
	});
	
	YAHOO.util.Event.on('divTwoButton', 'click', function() {
		slideInDivTwo();
	});
	
	YAHOO.util.Event.on('divTwoCloseButton', 'click', function() {
		slideOutDivTwo();
	});
	
	YAHOO.util.Event.on('divThreeButton', 'click', function() {
		slideInDivThree();
	});
	
	YAHOO.util.Event.on('divThreeCloseButton', 'click', function() {
		slideOutDivThree();
	});
	
	YAHOO.util.Event.on('divFourButton', 'click', function() {
		slideInDivFour();
	});
	
	YAHOO.util.Event.on('divFourCloseButton', 'click', function() {
		slideOutDivFour();
	});