create: function(dialog) {
            if (this.instances.length === 0) {
                // prevent use of anchors and inputs
                // we use a setTimeout in case the overlay is created from an
                // event that we're going to be cancelling (see #2804)
                setTimeout(function() {
                    // handle $(el).dialog().dialog('close') (see #4065)
                    if ($.ui.dialog.overlay.instances.length) {
                        $(document).bind($.ui.dialog.overlay.events, function(event) {
                            var parentDialog = $(event.target).parents('.ui-dialog');
                            if (parentDialog.length > 0) {
                                var parentDialogZIndex = parentDialog.css('zIndex') || 0;
                                return parentDialogZIndex > $.ui.dialog.overlay.maxZ;
                            }

                            var aboveOverlay = false;
                            $(event.target).parents().each(function() {
                                var currentZ = $(this).css('zIndex') || 0;
                                if (currentZ > $.ui.dialog.overlay.maxZ) {
                                    aboveOverlay = true;
                                    return;
                                }
                            });

                            return aboveOverlay;
                        });
                    }
                }, 1);

                // allow closing by pressing the escape key
                $(document).bind('keydown.dialog-overlay', function(event) {
                    (dialog.options.closeOnEscape && event.keyCode
						&& event.keyCode == $.ui.keyCode.ESCAPE && dialog.close(event));
                });

                // handle window resize
                $(window).bind('resize.dialog-overlay', $.ui.dialog.overlay.resize);
            }

            var $el = $('<div></div>').appendTo(document.body)
			.addClass('ui-widget-overlay').css({
			    width: this.width(),
			    height: this.height()
			});

            (dialog.options.bgiframe && $.fn.bgiframe && $el.bgiframe());

            this.instances.push($el);
            return $el;
        }