Since a couple of days ago I get the following message after every 1-2 minutes if I don't click anything in the game window.

"Hi! ♥
You didn't play for a long time, so your session ended.
Please reload Nutaku's page to continue playing!"

As the message says, I have to refresh the page every time I get this.

I don't see anyone mention it here, so is it only me who's getting this message?
If I'm not the only one, and it's an intentionally implemented timeout, then why?