diff --git a/source/clog-document.lisp b/source/clog-document.lisp
index 1d00ca9..45e3648 100644
--- a/source/clog-document.lisp
+++ b/source/clog-document.lisp
@@ -141,11 +141,28 @@ clog-document object. (Private)"))
 ;;;;;;;;;;;;;;;;;
 
 (defgeneric ready-state (clog-document)
-  (:documentation "Get ready-state."))
+  (:documentation "Get ready-state. Returns 'loading'|'interactive'|'complete'.
+The state would only change if the boot-page was still loading css, graphics, etc.
+Under normal circumstance there is no need in CLOG to check if the state is ready
+as on-new-window is only called once one can interact with page. See also
+SET-ON-READY-STATE-CHANGE"))
 
 (defmethod ready-state ((obj clog-document))
   (query obj "readyState"))
 
+;;;;;;;;;;;;;;;;;;;;;;
+;; visibility-state ;;
+;;;;;;;;;;;;;;;;;;;;;;
+
+(defgeneric visibility-state (clog-document)
+  (:documentation "Get visibility-state. Returns the string 'visible' if
+browser is in non-minmized state and is partialy visible and 'hidden' is
+browser is minimized or no part of page is visible including an OS screen
+lock."))
+
+(defmethod visibility-state ((obj clog-document))
+  (query obj "visibilityState"))
+
 ;;;;;;;;;;;;;;
 ;; load-css ;;
 ;;;;;;;;;;;;;;
@@ -286,3 +303,30 @@ If ON-FULL-SCREEN-CHANGE-HANDLER is nil unbind the event."))
 
 (defmethod set-on-full-screen-change ((obj clog-document) handler)
   (set-on-event obj "fullscreenchange" handler))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; set-on-visibility-change ;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defgeneric set-on-visibility-change (clog-document
+                                       on-visibility-change-handler)
+  (:documentation "Set the ON-VISIBILITY-CHANGE-HANDLER for CLOG-OBJ.
+If ON-VISIBILITY-CHANGE-HANDLER is nil unbind the event. This event
+is fired when the page visibility has changed such as a tab being
+switch of browser minimized. Use the VISIBILITY-STATE property to
+identify chage."))
+
+(defmethod set-on-visibility-change ((obj clog-document) handler)
+  (set-on-event obj "visibilitychange" handler))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; set-on-ready-state-change ;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defgeneric set-on-ready-state-change (clog-document
+                                       on-ready-state-change-handler)
+  (:documentation "Set the ON-READY-STATE-CHANGE-HANDLER for CLOG-OBJ.
+If ON-READY-STATE-CHANGE-HANDLER is nil unbind the event."))
+
+(defmethod set-on-ready-state-change ((obj clog-document) handler)
+  (set-on-event obj "readystatechange" handler))
diff --git a/source/clog-helpers.lisp b/source/clog-helpers.lisp
index ab7711b..883b815 100644
--- a/source/clog-helpers.lisp
+++ b/source/clog-helpers.lisp
@@ -92,12 +92,15 @@
 ;; clog-repl ;;
 ;;;;;;;;;;;;;;;
 
-(defun clog-repl (&key (clog-gui-initialize t) (clog-web-initialize t))
+(defun clog-repl (&key (clog-gui-initialize t)
+		    (clog-web-initialize t)
+		    (boot-file "/debug.html")
+		    (port 8080))
   "Set a path /repl that opens a blank page and sets the global
 clog-user:*body* to last window openned to /repl. Debug mode is
-set (logging to browser console), "
+set (logging to browser console) in the default debug.html boot-file."
   (unless *clog-running*
-    (initialize nil :boot-file "/debug.html"))
+    (initialize nil :boot-file boot-file :port port))
   (set-on-new-window (lambda (body)
                        (clog-connection:debug-mode (connection-id body))
                        (when clog-web-initialize
diff --git a/source/clog.lisp b/source/clog.lisp
index bbb1532..f6ea093 100644
--- a/source/clog.lisp
+++ b/source/clog.lisp
@@ -1010,6 +1010,7 @@ embedded in a native template application.)"
   (head-element     generic-function)
   (body-element     generic-function)
   (document-element generic-function)
+  (visibility-state generic-function)
   (ready-state      generic-function)
   (load-css         generic-function)
   (load-script      generic-function)
@@ -1020,6 +1021,8 @@ embedded in a native template application.)"
 
   "CLOG-Document - Events"
   (set-on-full-screen-change generic-function)
+  (set-on-visibility-change  generic-function)
+  (set-on-ready-state-change generic-function)
   (set-on-load-script        generic-function))
 
 (defsection @clog-navigator (:title "CLOG Navigator Objects")