[ninjin-carh]

I have found Leechblock useful in Firefox - it allows blocking or a delay before showing a page with a reminder this is a time waster site.... https://addons.mozilla.org/en-US/firefox/addon/leechblock-ng...

[taauji]

Leechblock is incredibly helpful and has saved my innumerable amount of unproductive hours. It is highly customisable.

[artemonster]

I love this addon!