var isNav, isIE;
var layerRef="";
var layerStyleRef = "";
var styleSwitch = "";
var LetterCount = 0;

if (navigator.appName == "Netscape")
	{
	isNav = true;	
	layerStyleRef=".";
	layerRef="document.layers"; 
	styleSwitch=""; 
	}
else
	{ 
	isIE = true;
	layerStyleRef=".style."; 
	layerRef="document.all"; 
	styleSwitch=".style"; 
	}

function ShowLayer(l)
	{
	eval(layerRef + '["' + l + '"]'+layerStyleRef+'display = ""');
	}
	
function HideLayer(l)
	{
	eval(layerRef + '["' + l + '"]'+layerStyleRef+'display = "none"');
	}

function ShowRocks(f)
	{
	for (i=1;i<f.elements.length;i++)
	  if (f.elements[i-1].checked) ShowLayer("d"+i);
	    else HideLayer("d"+i);
	}
function HidePeople(n)
	{
	for (i=1;i<n+1;i++) HideLayer("d"+i);
	if (LetterCount==0) LetterCount = n;
	}
function ShowPeople(l)
	{
	HidePeople(LetterCount);
	ShowLayer(l);
	}
function ShowAllPeople()
	{
	for (i=1;i<LetterCount+1;i++) ShowLayer("d"+i);
	}