In KDE (Gnome does that too), whenever you press the ‘Power’ button or try to Logout/Reboot or Shutdown the computer using the start-menu, you’ll be greeted with a dialog box asking you to reconfirm the changes.
In general this is a good thing, because if you’re in the middle of doing something, and accidentally clicked any of those options (say while browsing the start-menu for example), then you’ll still have the chance to Cancel it. But then again, it can be a bit of a pain in the as* too :).
Though in Gnome you cannot disable it that easily, but in KDE, and it being well known for its ‘features richness’, you can disable this confirmation dialog box quite easily.
Note: (I’m using the KDE 4.8.2 and Kubuntu 12.04. If you’re using much older versions of KDE, then the procedure should be a bit different).
1. First, click on the start-menu icon in KDE and search for ‘System settings’, then click on its icon and open that window.
2. Then, from the ‘System settings’ window, scroll down a little bit, and under the sub option ‘System Administration’, click (or double click, depending on your configuration) on the icon that says ‘Startup and Shutdown’.
3. Then from the new window you get, from your left, click on ‘Session Management’. Then from the right side, remove the ‘check mark’ on the option called ‘Confirm logout’.
After that, click on the ‘Apply’ button and close that window.
That’s it!. Now whenever you click on any of those actions (not just ‘logout’), you won’t have to reconfirm anymore.
But please remember that, once you’ve done this, though some applications such as ‘Kate’ (text editor) will still ‘block’ and ask you whether you’d like to save your changes before you logout etc, other applications such as Mozilla Firefox for instance, won’t be able to block logout/reboot/shutdown processes.
So use it with caution :). Good luck.