lad@ubuntu:~$ desktop-file-validate /usr/share/applications/*.desktop
/usr/share/applications/checkbox-gui.desktop: error: value "System;Qt;Application" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/compiz.desktop: warning: key "Encoding" in group "Desktop Entry" is deprecated
/usr/share/applications/credentials-preferences.desktop: error: value "Unity" for string list key "NotShowIn" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/debian-uxterm.desktop: hint: value "System;TerminalEmulator;Utility;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/debian-xterm.desktop: hint: value "System;TerminalEmulator;Utility;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/evince.desktop: hint: value "GNOME;GTK;Office;Viewer;Graphics;2DGraphics;VectorGraphics;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/evince-previewer.desktop: hint: value "GNOME;GTK;Office;Viewer;Graphics;2DGraphics;VectorGraphics;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/gedit.desktop: warning: key "OnlyShowIn" in group "Desktop Action Window" is deprecated
/usr/share/applications/gedit.desktop: warning: key "OnlyShowIn" in group "Desktop Action Document" is deprecated
/usr/share/applications/gnome-screenshot.desktop: error: value "Screen;Window;Area" for string list key "Actions" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/gnome-screenshot.desktop: warning: key "OnlyShowIn" in group "Desktop Action Screen" is deprecated
/usr/share/applications/gnome-screenshot.desktop: warning: key "OnlyShowIn" in group "Desktop Action Window" is deprecated
/usr/share/applications/gnome-screenshot.desktop: warning: key "OnlyShowIn" in group "Desktop Action Area" is deprecated
/usr/share/applications/gnome-screenshot.desktop: error: action group "Desktop Action Window" exists, but there is no matching action "Window"
/usr/share/applications/gnome-screenshot.desktop: error: action group "Desktop Action Screen" exists, but there is no matching action "Screen"
/usr/share/applications/gnome-screenshot.desktop: error: action group "Desktop Action Area" exists, but there is no matching action "Area"
/usr/share/applications/guake.desktop: hint: value "GNOME;GTK;System;Utility;TerminalEmulator;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/guake-prefs.desktop: warning: key "Encoding" in group "Desktop Entry" is deprecated
/usr/share/applications/im-config.desktop: error: value "keyboard;input" for locale string list key "Keywords" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/im-config.desktop: error: value "Settings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/language-selector.desktop: error: value "GNOME;GTK;Settings;DesktopSettings;X-GNOME-Settings-Panel;X-Unity-Settings-Panel;X-GNOME-PersonalSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/nautilus.desktop: hint: value item "FileManager" in key "Categories" in group "Desktop Entry" can be extended with another category among the following categories: System;FileTools
/usr/share/applications/nautilus.desktop: warning: key "OnlyShowIn" in group "Desktop Action Window" is deprecated
/usr/share/applications/nautilus-home.desktop: hint: value "GNOME;GTK;Core;" for key "Categories" in group "Desktop Entry" does not contain a registered main category; application might only show up in a "catch-all" section of the application menu
/usr/share/applications/nautilus-home.desktop: warning: key "OnlyShowIn" in group "Desktop Action Window" is deprecated
/usr/share/applications/signon-ui-browser-process.desktop: warning: key "Encoding" in group "Desktop Entry" is deprecated
/usr/share/applications/software-properties-drivers.desktop: error: file contains key "NotShownIn" in group "Desktop Entry", but keys extending the format should start with "X-"
/usr/share/applications/software-properties-drivers.desktop: error: value "X-XFCE;GTK;Settings;HardwareSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/system-config-printer.desktop: hint: value "GNOME;GTK;Settings;HardwareSettings;X-GNOME-Settings-Panel;X-Unity-Settings-Panel;System;Printing;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/ubuntu-software-center.desktop: hint: value "PackageManager;GTK;System;Settings;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/unity-appearance-panel.desktop: error: value "GNOME;GTK;Settings;DesktopSettings;X-Unity-Settings-Panel;X-GNOME-PersonalSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/unity-color-panel.desktop: error: value "GNOME;GTK;Settings;X-Unity-Settings-Panel;HardwareSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/unity-datetime-panel.desktop: hint: value "GNOME;GTK;Utility;DesktopSettings;Settings;X-GNOME-SystemSettings;X-Unity-Settings-Panel;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/unity-power-panel.desktop: error: value "GNOME;GTK;Settings;DesktopSettings;X-Unity-Settings-Panel;HardwareSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/unity-region-panel.desktop: error: value "GNOME;GTK;Settings;DesktopSettings;X-Unity-Settings-Panel;X-GNOME-PersonalSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/unity-screen-panel.desktop: error: value "GNOME;GTK;Settings;DesktopSettings;X-Unity-Settings-Panel;X-GNOME-PersonalSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/unity-tweak-tool.desktop: warning: key "OnlyShowIn" in group "Desktop Action Unity" is deprecated
/usr/share/applications/unity-tweak-tool.desktop: warning: key "OnlyShowIn" in group "Desktop Action WinMng" is deprecated
/usr/share/applications/unity-tweak-tool.desktop: warning: key "OnlyShowIn" in group "Desktop Action Appearance" is deprecated
/usr/share/applications/unity-tweak-tool.desktop: warning: key "OnlyShowIn" in group "Desktop Action System" is deprecated
/usr/share/applications/unity-user-accounts-panel.desktop: error: value "System;Settings;X-Unity-Settings-Panel;X-GNOME-SystemSettings" for string list key "Categories" in group "Desktop Entry" does not have a semicolon (';') as trailing character
/usr/share/applications/update-manager.desktop: hint: value "System;Settings;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu
/usr/share/applications/xdiagnose.desktop: hint: value "System;Settings;" for key "Categories" in group "Desktop Entry" contains more than one main category; application might appear more than once in the application menu

lad@ubuntu:/usr/share/applications$ cat checkbox-gui.desktop 
[Desktop Entry]
Name=System Testing
Type=Application
Comment=Test your systems compatibility with Ubuntu.
Exec=checkbox-gui
Icon=checkbox
Categories=System;Qt;Application
Keywords=testing;drivers;hardware;
X-GNOME-Gettext-Domain=checkbox
X-Ayatana-Appmenu-Show-Stubs=False
X-Ubuntu-Touch=true
X-Ubuntu-StageHint=SideStage