To uninstall xscreensaver-screensaver-webcollage just follow these instructions.
sudo apt-get remove xscreensaver-screensaver-webcollage
This will remove just the xscreensaver-screensaver-webcollage package itself.
sudo apt-get remove --auto-remove xscreensaver-screensaver-webcollage
This will remove the xscreensaver-screensaver-webcollage package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for xscreensaver-screensaver-webcollage then this will work.
sudo apt-get purge xscreensaver-screensaver-webcollage
Or similarly, like this xscreensaver-screensaver-webcollage
sudo apt-get purge --auto-remove xscreensaver-screensaver-webcollage
|Maintainer||Tormod Volden <email@example.com>|
|Home page||http://www.jwz.org/xscreensaver/ x11::screensaver|
|Description||Webcollage screen saver module from XScreenSaver web searches on the Internet.|