diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # pgdl
 
-a terminal user interface program that downloads a video from html and call vlc to play it immediately.
-(Linux: vlc -f "video.mp4", MACOSX: open "video.mp4" -a vlc)
+a terminal user interface program that downloads a video (or a file) from webpage and xdg-open it immediately.
+(Linux: xdg-open "video.mp4", MACOSX: open "video.mp4")
 
 Client: Only for Linux and MACOSX.
 Server: Only for nginx's file download page.
@@ -10,22 +10,18 @@
 
 ## Installing
 
-cabal update <br>
+cabal update  
 cabal install pgdl
 
 ## Shortcut keys
 
-q - quit
-<br>
-s - list files that similar with the highlighted video
-<br>
-Key Right - show the detailed information of the highlighted video
-<br>
-Key Left - go back to the previous page
-<br>
-Enter - play the video
-<br>
-/ - open a input box to enter a keyword to search
-<br>
-n - sort the current list by name
+q - quit  
+s - list files that similar with the highlighted video  
+Key Right - show the detailed information of the highlighted video  
+Key Left - go back to the previous page  
+Enter - play the video  
+/ - open a input box to enter a keyword to search  
+n - sort the current list by name  
+v - show the videos already in the disk  
+u - show the videos not in the disk
 
diff --git a/pgdl.cabal b/pgdl.cabal
--- a/pgdl.cabal
+++ b/pgdl.cabal
@@ -1,6 +1,6 @@
 
 name:                pgdl
-version:             8.2
+version:             8.3
 license:             PublicDomain
 license-file:        LICENSE
 author:              sifmelcara
@@ -15,11 +15,11 @@
                      Client: Only for Linux and MACOSX.
                      Server: Only for nginx's file download page.
                      .
-                     The program will sort the video files and folders by date while files in nginx's download page just sort by name.
+                     The program will sort the files and folders by date while files in nginx's download page just sort by name.
                      .
                      For shortcut keys, please visit <https://github.com/sifmelcara/pgdl>
 
-synopsis:            simply download a video from webpage and play it.
+synopsis:            simply download a video (or a file) from a webpage and xdg-open it.
 
 source-repository head
   type:     git
@@ -34,7 +34,7 @@
   build-depends:       base == 4.*, process, 
                        directory, bytestring,
                        tagsoup, network-uri, 
-                       vty, text, vty-ui >= 1.8,
+                       vty, text, vty-ui >= 1.9,
                        configurator >= 0.3.0.0, HTTP,
                        filepath, Cabal, array
   ghc-options:         -threaded -O2
diff --git a/src/Pgdl.hs b/src/Pgdl.hs
--- a/src/Pgdl.hs
+++ b/src/Pgdl.hs
@@ -57,12 +57,16 @@
 
     ifsfg <- newFocusGroup
     -- a focus group for information page
+    
+    helpfg <- newFocusGroup
+    -- a focus group of help page
 
     -- this function will show the focused item's information to user
 
     tmpLfg `onKeyPressed` tryExit
     dfcg `onKeyPressed` tryExit
     ifsfg `onKeyPressed` tryExit
+    helpfg `onKeyPressed` tryExit
 
     -- colorDecide tmpLst
 
@@ -142,6 +146,12 @@
                     return True
                 _     -> return False
 
+            let chgHelp = do
+                  hp <- centered =<< plainText helpPage
+                  addToFocusGroup helpfg hp
+                  join $ addToCollection c hp helpfg
+            onKeyPressed helpfg $ \_ _ _ -> (chgls >> return True)
+
             onKeyPressed lst $ \_ key _ -> case key of
                 KRight -> do
                     chgInf
@@ -189,9 +199,17 @@
                     filterVListIO vlst $ \obj -> if isVid obj then downloaded obj
                                                  else return False 
                     return True
+                KChar 'u' -> do
+                    filterVListIO vlst $ \obj -> if isVid obj then not <$> (downloaded obj)
+                                                 else return False 
+                    return True
                 KChar '/' -> do
                     chgky
                     return True
+                KChar 'h' -> do
+                    chgHelp
+                    return True
+
                 _   -> return False
 
             return ()
@@ -200,4 +218,18 @@
     runUi c $ defaultContext { normalAttr = white `on` black 
                              , focusAttr  = black `on` blue
                              }
+
+helpPage :: T.Text
+helpPage = T.unlines [ 
+                      "q - quit"
+                     ,"s - list files that similar with the highlighted video"
+                     ,"Key Right - show the detailed information of the highlighted video"
+                     ,"Key Left - go back to the previous page"
+                     ,"Enter - play the video"
+                     ,"/ - open a input box to enter a keyword to search"
+                     ,"n - sort the current list by name"
+                     ,"v - show the videos already in the disk"
+                     ,"u - show the videos not in the disk"
+                     ]
+
 
diff --git a/src/PrsVid.hs b/src/PrsVid.hs
--- a/src/PrsVid.hs
+++ b/src/PrsVid.hs
@@ -19,7 +19,7 @@
          filter isVidLn . map parseTags . T.lines
     where isVidLn = any isVidLnk
           isVidLnk tg
-            | isTagOpen tg = any (`T.isSuffixOf` fromAttrib "href" tg) fmts
+            | isTagOpen tg = (not $ "/" `T.isSuffixOf` fromAttrib "href" tg) && (not . T.null $ fromAttrib "href" tg)
             | otherwise = False
           pullText tg
             | isTagOpen tg = fromAttrib "href" tg
diff --git a/src/RealWorld.hs b/src/RealWorld.hs
--- a/src/RealWorld.hs
+++ b/src/RealWorld.hs
@@ -40,7 +40,7 @@
     checkFile
     case buildOS of
         OSX   -> runCommand $ "open " ++ addq localloc ++ " "
-        Linux -> runCommand $ "xdg-open " ++ addq localloc ++ " &>/dev/null &"
+        Linux -> runCommand $ "nohup xdg-open " ++ addq localloc ++ " &>/dev/null &"
         _     -> error "OS unsupported!"
     return ()
   where vn = T.unpack . vidName $ vid
@@ -56,7 +56,7 @@
     let localloc = localdir </> vn
     case buildOS of
         OSX   -> runCommand $ "open " ++ addq localloc ++ " "
-        Linux -> runCommand $ "xdg-open " ++ addq localloc ++ " &>/dev/null &"
+        Linux -> runCommand $ "nohup xdg-open " ++ addq localloc ++ " &>/dev/null &"
         _     -> error "OS unsupported!"
     return ()
     -- exitSuccess