function showLayer(whichLayer) {
	if (document.getElementById) {
		// this is the way the standards work
		var style2 = document.getElementById(whichLayer).style;
		style2.display = "block";
	} else if (document.all) {
		// this is the way old msie versions work
		var style2 = document.all[whichLayer].style;
		style2.display = "block";
	} else if (document.layers) {
		// this is the way nn4 works
		var style2 = document.layers[whichLayer].style;
		style2.display = "block";
	}
}
function hideLayer(whichLayer) {
	if (document.getElementById) {
		// this is the way the standards work
		var style2 = document.getElementById(whichLayer).style;
		style2.display = "none";
	} else if (document.all) {
		// this is the way old msie versions work
		var style2 = document.all[whichLayer].style;
		style2.display = "none";
	} else if (document.layers) {
		// this is the way nn4 works
		var style2 = document.layers[whichLayer].style;
		style2.display = "none";
	}
}
function toggleLayer(whichLayer) {
	if (document.getElementById) {
		// this is the way the standards work
		var style2 = document.getElementById(whichLayer).style;
		style2.display = style2.display? "":"block";
	} else if (document.all) {
		// this is the way old msie versions work
		var style2 = document.all[whichLayer].style;
		style2.display = style2.display? "":"block";
	} else if (document.layers) {
		// this is the way nn4 works
		var style2 = document.layers[whichLayer].style;
		style2.display = style2.display? "":"block";
	}
}

var origWidth, origHeight;
if (document.layers) {
	origWidth = window.innerWidth; origHeight = window.innerHeight;
	window.onresize = function() { if (window.innerWidth != origWidth || window.innerHeight != origHeight) history.go(0); }
}

var cur_lyr;	// holds id of currently visible layer
function swapLayers(id) {
  if (cur_lyr) hideLayer(cur_lyr);
  showLayer(id);
  cur_lyr = id;
}

function showLayer(id) {
  var lyr = getElemRefs(id);
  if (lyr && lyr.css) {
	lyr.css.display = "block";
	lyr.css.visibility = "visible";
  }
}

function hideLayer(id) {
  var lyr = getElemRefs(id);
  if (lyr && lyr.css) {
	  lyr.css.display = "none";
	  lyr.css.visibility = "hidden";
  }
}

function getElemRefs(id) {
	var el = (document.getElementById)? document.getElementById(id): (document.all)? document.all[id]: (document.layers)? document.layers[id]: null;
	if (el) el.css = (el.style)? el.style: el;
	return el;
}