function MM_showHideLayers() {
  if(tp > 0 || bp > 0 || up > 0)
        return;
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { obj=obj.style; v=(v=='show')?'visible':(v=='hide')?'hidden':v; }
    obj.visibility=v; 
    obj.display=((v=='visible')?'':((v=='hidden')?'none':v)); }
}

var tp=0, bp=0, up=0;
function MM_stayShownLayer(imgName) { //v6.0
    ClearSelection();
    MM_showHideLayers(imgName,'','show');

    if(imgName == 'i001'){
        tp = 1;
        document.getElementById('frmSelection').txtSelection.value = "Tri-Point Series";
    }else if(imgName == 'i002'){
        bp = 1;
        document.getElementById('frmSelection').txtSelection.value = "Bi-Point Series";
    }else if(imgName == 'i003'){
        up = 1;
        document.getElementById('frmSelection').txtSelection.value = "Uni-Point Series";
    }
    document.getElementById('frmSelection').txtImage.value = imgName;
}
...

<div id="i001" style="position:relative; width:200px; height:115px; z-index:1; left: 0; top: 0; visibility: hidden; display:none;"><img src="images/i001.jpg" width="487" height="287" border="0" usemap="#Map5"></div>

<div id="i002" style="position:relative; width:200px; height:115px; z-index:2; left: 0; top: 0; visibility: hidden; display:none;"><img src="images/i002.jpg" width="487" height="287" border="0" usemap="#Map6"></div>

<div id="i003" style="position:relative; width:200px; height:115px; z-index:3; left: 0; top: 0; visibility: hidden; display:none;"><img src="images/i003.jpg" width="487" height="287" border="0" usemap="#Map7"></div>
...
<form id="frmSelection" action="step2.php" method="post">
              <font face="Arial, Helvetica, sans-serif" size="2">Cabinet Style 
              Selected</font> 
              <input type="text" name="txtSelection" value="<?php echo ((isset($_SESSION['step1SelText'][$cabindex])) ? $_SESSION['step1SelText'][$cabindex] : 'not yet selected') ?>" readonly>
              <input type="hidden" name="txtImage" value="<?php echo ((isset($_SESSION['step1SelImg'][$cabindex])) ? $_SESSION['step1SelImg'][$cabindex] : '') ?>" readonly>
              <font face="Arial, Helvetica, sans-serif" size="2" color="#999999">(Click 
              on icon to select)</font> 
            </form>