function getViewPortSize() {
	// the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight

  if (typeof window.innerWidth != 'undefined')
  {
       viewportwidth = window.innerWidth,
       viewportheight = window.innerHeight
  }

// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)

  else if (typeof document.documentElement != 'undefined'
      && typeof document.documentElement.clientWidth !=
      'undefined' && document.documentElement.clientWidth != 0)
  {
        viewportwidth = document.documentElement.clientWidth,
        viewportheight = document.documentElement.clientHeight
  }

  // older versions of IE

  else
  {
        viewportwidth = document.getElementsByTagName('body')
[0].clientWidth,
        viewportheight = document.getElementsByTagName('body')
[0].clientHeight
  }
}

function grayOut(vis, options) {
   // Pass true to gray out screen, false to ungray
   // options are optional.  This is a JSON object with the following (optional) properties
   // opacity:0-100         // Lower number = less grayout higher =  more of a blackout
   // zindex: #             // HTML elements with a higher zindex appear on top of the gray out
   // bgcolor: (#xxxxxx)    // Standard RGB Hex color code
   // grayOut(true, {'zindex':'50', 'bgcolor':'#0000FF', 'opacity':'70'});
   // Because options is JSON opacity/zindex/bgcolor are all optional and can appear
   // in any order.  Pass only the properties you need to set.
   var options = options || {};
   var zindex = options.zindex || 50;
   var opacity = options.opacity || 70;
   var opaque = (opacity / 100);
   var bgcolor = options.bgcolor || '#000000';
   var dark=document.getElementById('darkenScreenObject');
   if (!dark) {
     // The dark layer doesn't exist, it's never been created.  So we'll
     // create it here and apply some basic styles.
     // If you are getting errors in IE see: http://support.microsoft.com/default.aspx/kb/927917
     var tbody = document.getElementsByTagName("body")[0];
     var tnode = document.createElement('div');           // Create  the layer.
         tnode.style.position='absolute';                 // Position  absolutely
         tnode.style.top='0px';                           // In the top
         tnode.style.left='0px';                          // Left  corner of the page
         tnode.style.overflow='hidden';                   // Try to  avoid making scroll bars
         tnode.style.display='none';                      // Start out  Hidden
         tnode.id='darkenScreenObject';                   // Name it  so we can find it later
     tbody.appendChild(tnode);                            // Add it to  the web page
     dark=document.getElementById('darkenScreenObject');  // Get the object.
   }
   if (vis) {
	getViewPortSize();
	var percent = false;
     // Calculate the page width and height
     if( document.body && ( document.body.scrollWidth || document.body.scrollHeight ) ) {
         var pageWidth = document.body.scrollWidth;
         var pageHeight = document.body.scrollHeight;
     } else if( document.body.offsetWidth ) {
       var pageWidth = document.body.offsetWidth;
       var pageHeight = document.body.offsetHeight;
     } else {
        var pageWidthF='100%';
        var pageHeightF='100%';
	   var percent = true;
     }
	if(!percent) {
		if(pageWidth<viewportwidth-20) {
			pageWidthF = viewportwidth + 'px';	
		} else {
			pageWidthF = pageWidth + 'px';	
		}
		if(pageHeight<viewportheight) {
			pageHeightF = viewportheight + 'px';
		} else {
			pageHeightF = pageHeight + 'px';	
		}
	}
     //set the shader to cover the entire page and make it visible.
     dark.style.opacity=opaque;
     dark.style.MozOpacity=opaque;
     dark.style.filter='alpha(opacity='+opacity+')';
     dark.style.zIndex=zindex;
     dark.style.backgroundColor=bgcolor;
     dark.style.width= pageWidthF;
     dark.style.height= pageHeightF;
     dark.style.display='block';
   } else {
      dark.style.display='none';
   }
}