var initialised = false;
var lastButton;
var lastLayer;

function showObject(obj) {
  if (is.ns) obj.visibility = "show"
  else if (is.ie) obj.style.visibility = "visible"
}
function hideObject(obj) {
  if (is.ns) obj.visibility = "hide"
  else if (is.ie) obj.style.visibility = "hidden"
} 
function changeButton(obj,lyr) {
  if (is.ns) obj.visibility = "hide" //hide the clicked button
  else if (is.ie) obj.style.visibility = "hidden"
  if (is.ns) lyr.visibility = "show" //show the clicked buttons sub layer
  else if (is.ie) lyr.style.visibility = "visible"
  if (lastLayer != lyr) { //if the last layer selected is not the same as this one
	  if (initialised == false) {
		initialised = true;
	  } else {
	    if (is.ns) lastButton.visibility = "show" //show the last clicked button
		else if (is.ie) lastButton.style.visibility = "visible"
		if (is.ns) lastLayer.visibility = "hide" //hide the last sub layer
		else if (is.ie) lastLayer.style.visibility = "hidden"
	  }
  }
  lastLayer = lyr
  lastButton = obj
}