Howto Grey-Out The Screen (ing)

<script type="text/javascript">
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) {
    // Calculate the page width and height
    if( document.body && ( document.body.scrollWidth || document.body.scrollHeight ) ) {
        var pageWidth = document.body.scrollWidth+'px';
        var pageHeight = document.body.scrollHeight+'px';
    } else if( document.body.offsetWidth ) {
      var pageWidth = document.body.offsetWidth+'px';
      var pageHeight = document.body.offsetHeight+'px';
    } else {
      var pageWidth='100%';
      var pageHeight='100%';
    } 
    //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= pageWidth;
    dark.style.height= pageHeight;
    dark.style.display='block';                         
  } else {
    dark.style.display='none';
  }
}
</script>

<A HREF="#" onclick="grayOut(true); alert('Example!'); grayOut(false); return false;" class='popup'>Example</A>