function changeTab(whichLayer, newImage, newImageSrc) {

	//change the image to it's original
	swapImage(currentImage,'',currentImageSrc,1);
	
	//change the image
	currentImage = newImage;
	currentImageSrc = document.getElementById(newImage).src;
	swapImage(newImage,'',newImageSrc,1);

	//hide the currentTab
	document.getElementById(currentTab).style.display = "none";	
	
	//change the content
	document.getElementById(whichLayer).style.display = "block";
	currentTab = whichLayer;
}