function showLayer( layerId) {
	var thisLayer = document.getElementById( layerId );
	if (thisLayer == null) {
		return false;
	}
	thisLayer.style.visibility = 'visible';
	thisLayer.style.display = 'block';
	}
	
function hideLayer( layerId) {
	var thisLayer = document.getElementById( layerId );
	if (thisLayer == null) {
		return false;
	}
	thisLayer.style.visibility = 'hidden';
	thisLayer.style.display = 'none';
	}
	
function hideAll() {
hideLayer('SM_Intro');
hideLayer('SM_SD1');
hideLayer('SM_SD2');
hideLayer('SM_SD3');
hideLayer('SM_SD4');
hideLayer('SM_SD5');
hideLayer('SM_SD6');
hideLayer('SM_SD7');
hideLayer('SM_SD8');
hideLayer('SM_SD9');
hideLayer('SM_SD10');
hideLayer('SM_SD11');
	}

function nextSection(curLayerID, sectionFldFlg, nextLayerID) {
	hideLayer(curLayerID);
	markSectionComplete(sectionFldFlg);
	showLayer(nextLayerID);
	}

function goMenu(curLayerID) {
	hideLayer(curLayerID);
	showLayer('SM_Intro');
	}

function goMenuComplete(curLayerID, sectionFldFlg) {
	hideLayer(curLayerID);
	markSectionComplete(sectionFldFlg);
	markSectionComplete('SM_Status');
	showLayer('SM_Intro');
	}

function markSectionComplete(sectionFldFlg) {
	var thisSection=document.getElementById( sectionFldFlg );
	thisSection.value='1';
	}


*/showLayer and hideLayer with null catch /* 
function showLayer( layerId) {
  var thisLayer = document.getElementById( layerId );
  if (thisLayer == undefined) {
    return false;
   } else {
     thisLayer.style.visibility = 'visible';
     thisLayer.style.display = 'block';
   }
 }
 
function hideLayer( layerId) {
  var thisLayer = document.getElementById( layerId );
  if (thisLayer == undefined) {
    return false;
   } else {
     thisLayer.style.visibility = 'hidden';
     thisLayer.style.display = 'none';
   }
 }