function changeImg(obj, state) {
	if (state) {
		obj.src = obj.src.replace(/off/, "over");
	}
	else {
		obj.src = obj.src.replace(/over/, "off");
	}
}

function changeLayer(layerName) {
	// hide all text layers
	var allLayers = document.getElementById("rightContent").getElementsByTagName("div");
	for (var i=0; i<allLayers.length; i++) {
		allLayers[i].style.display = "none";
	}
	// hide all on buttons
	var allButtons = document.getElementById("subnav").getElementsByTagName("a");
	for (var i=0; i<allButtons.length; i++) {
		var currentButton = allButtons[i];
		currentButton.className = 'sub';
	}	
	// show selected text layer, list and title layer
	document.getElementById(layerName).style.display = "block";
	var listDiv = layerName + 'List';
	document.getElementById(listDiv).style.display = "block";
	var titleDiv = layerName + 'Title';
	document.getElementById(titleDiv).style.display = "block";
	// show selected button
	var button = layerName + 'B';
	document.getElementById(button).className = 'subActive';
}