function myGB_show_center(caption, url, /* optional */ height, width, callback_fn) {
   		  
  				var currentDate = new Date()
  				var options = {
            caption: caption,
            height: height || 500,
            width: width || 500,
            fullscreen: false,
            callback_fn: callback_fn,
    				show_loading: false,
    				salt: currentDate.getTime(),
    				center_win: true
      		}
          var win = new GB_Window(options);
          return win.show(url);
					
}