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';
    }
}