This is an avast file (used by the web shield and protected by the avast self-defence module) in the temp sub-folder that avast uses to scan content.

Files\Folders moved on Reboot... File move failed. C:\Windows\temp\_avast_\Webshlock.txt scheduled to be moved on reboot.

So in a way a good job that it failed, however, had it been removed it should have been recreated when you started browsing again.