/* Show / hide a layer depending on its style */
function showLayer (layerID) {
	var style = document.getElementById(layerID).style;
	style.display = style.display == "block" ? "none" : "block";
}

/* Switch between two text values */
function switchText (layerID,value1,value2) {
	var itm = document.getElementById(layerID).firstChild;
	itm.data = itm.data == value1 ? value2 : value1;
}