var GB_ROOT_DIR = "/greybox/";

	  GB_Show = function(caption, url, height, width, callback_fn) {
	             var options = {
	                 caption: caption,
	                 height: 550,
	                 width: 900,
	                 fullscreen: false,
	                 show_loading: true,
	                 callback_fn: callback_fn
	             }
	             var win = new GB_Window(options);
	             return win.show(url);
	  }