Time to time when I try to like some post,a window pops up and says 'An error occured' ,but after refreshing the page it doesn't happen anymore.Is it a bug?
Had it happen once or twice. As you can see, though, the error message is less helpful than even Windows, so I didn't let it concern me any further.
I have two guesses:
Your security token―the proof of authentication that you're viewing any given page as a logged-in member named |♚| KK |♚| and not someone else―had somehow expired when you tried to click the Like button. It gets renewed every 15 minutes or so. It's possible that the security token got renewed sometime between you opening the thread where you wanted to Like a post and clicking the Like button. If this is the case, the Like system (which is obviously unusable without logging in) may get confused as it sees you being logged in but can't determine who you are. .
Normal connection lag/hiccup whether from your side or ours.
In any case, simply reloading the page should totally fix it.