function changeTab(whichLayer) {
	var divit = getElementsByTagName('div');
	formatElements(divit);
	if (document.getElementById) {
		if(whichLayer == "tab1"){
		var element = document.getElementById(whichLayer);
		if(element != null){
		var style = element.style;
		style.display = style.display = "block";
		}
		document.getElementById('tab1link').className = "chosen";
		document.getElementById('tab2link').className = "";
		}if(whichLayer == "tab2"){
		var element = document.getElementById(whichLayer);
		if(element != null){
		var style = element.style;
		style.display = style.display = "block";
		}
		document.getElementById('tab2link').className = "chosen";
		document.getElementById('tab1link').className = "";
		}
	}
}
function getElementsByTagName(tag){		
		return document.getElementsByTagName(tag);
}
function formatElements(elements){
	for (i=0; i<elements.length; i++) {
		if(elements[i].id == "tab1"){
			var style = elements[i].style;
			style.display = "none";
			}
		else if(elements[i].id == "tab2"){
			var style = elements[i].style;
			style.display = "none";
			}
		}
}