function grayOut(vis, options) {
  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) {
    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+100+'px';
        var pageHeight = document.body.scrollHeight+100+'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';
  }

}