var lastLayer;		
	
	function show_layer(layer)
	{
		xDisplay(layer,"block");
			
	}
	function hide_layer(layer)
	{
		xDisplay(layer,"none");
	}
	
	//used to hide and show a layer based on clicking of a checkbox
	function toggle_single_layer(layer)
	{
		
		if(!xDisplay(layer))
		{
			xDisplay(layer,"block");
		}else
		{
			xDisplay(layer,"none");			
		}		
	}
	
	function toggle_layer(layer, hide_same)	
	{
        
		if(xDisplay(layer) == "none")
		{		    				
			xDisplay(layer,"block");
			if(lastLayer != 'na')
			{	
			    xDisplay(lastLayer,"none");	
			}
			
			lastLayer = layer;			
		}
		else
		{							
			
			if(hide_same && layer == lastLayer)
			{	
				xDisplay(layer,"none");
				layer = "na";
			}
		}
		
		//setTimeout("scrollToLayer('" + layer +"');", 250);		
		
	}
	function swap_layers(layer1, layer2)	
	{
		
		if(!xDisplay(layer1))
		{
			xDisplay(layer1,"block");
		}
		else
		{
			xDisplay(layer1,"none");
		}
		if(!xDisplay(layer2))
		{
			xDisplay(layer2,"block");
		}
		else
		{
			xDisplay(layer2,"none");
		}

	}