Newbie Popup window- Parent window issue

So you’ll have to bear with me since the site I’m working on I’ve inherited and I’ve only just started to mess around with javascript so my understanding of it ranges from rudimentary to nonexistent.

We have a link on our site that pulls up a page from our in-house server so people can check availability before making a reservation. It uses javascript for the popup but the problem is when you click on the parent window and navigate away it closes the popup. It would be nice if people could keep the availability page open while looking through the site at the different cabins. I’ve included a link the page in question and the javascript below. Thanks in advance for any help and patience.

function GP_AdvOpenWindow(theURL,winName,features,popWidth,popHeight,winAlign,ignorelink,alwaysOnTop,autoCloseTime,borderless) { //v2.0
  var leftPos=0,topPos=0,autoCloseTimeoutHandle, ontopIntervalHandle, w = 480, h = 340;  
  if (popWidth > 0) features += (features.length > 0 ? ',' : '') + 'width=' + popWidth;
  if (popHeight > 0) features += (features.length > 0 ? ',' : '') + 'height=' + popHeight;
  if (winAlign && winAlign != "" && popWidth > 0 && popHeight > 0) {
    if (document.all || document.layers || document.getElementById) {w = screen.availWidth; h = screen.availHeight;}
		if (winAlign.indexOf("center") != -1) {topPos = (h-popHeight)/2;leftPos = (w-popWidth)/2;}
		if (winAlign.indexOf("bottom") != -1) topPos = h-popHeight; if (winAlign.indexOf("right") != -1) leftPos = w-popWidth; 
		if (winAlign.indexOf("left") != -1) leftPos = 0; if (winAlign.indexOf("top") != -1) topPos = 0; 						
    features += (features.length > 0 ? ',' : '') + 'top=' + topPos+',left='+leftPos;}
  if (document.all && borderless && borderless != "" && features.indexOf("fullscreen") != -1) features+=",fullscreen=1";
  if (window["popupWindow"] == null) window["popupWindow"] = new Array();
  var wp = popupWindow.length;
  popupWindow[wp] = window.open(theURL,winName,features);
  if (popupWindow[wp].opener == null) popupWindow[wp].opener = self;  
  if (document.all || document.layers || document.getElementById) {
    if (borderless && borderless != "") {popupWindow[wp].resizeTo(popWidth,popHeight); popupWindow[wp].moveTo(leftPos, topPos);}
    if (alwaysOnTop && alwaysOnTop != "") {
    	ontopIntervalHandle = popupWindow[wp].setInterval("window.focus();", 50);
    	popupWindow[wp].document.body.onload = function() {window.setInterval("window.focus();", 50);}; }
    if (autoCloseTime && autoCloseTime > 0) {
    	popupWindow[wp].document.body.onbeforeunload = function() {
  			if (autoCloseTimeoutHandle) window.clearInterval(autoCloseTimeoutHandle);
    		window.onbeforeunload = null;	}  
   		autoCloseTimeoutHandle = window.setTimeout("popupWindow["+wp+"].close()", autoCloseTime * 1000); }
  	window.onbeforeunload = function() {for (var i=0;i<popupWindow.length;i++) popupWindow[i].close();}; }   
  document.MM_returnValue = (ignorelink && ignorelink != "") ? false : true;
}

and the link

<a style="text-decoration:underline;" target="blank" href="javascript:; " onClick="GP_AdvOpenWindow('getPage.php?page=oHutAvail.asp&hsID=1,3','tenth','fullscreen=no,toolbar=yes,location=no,status=no,menubar=yes,scrollbars=yes,resizable=yes',620,525,'topcenter','ignoreLink','',30,'');return document.MM_returnValue">