How do I block access to certain websites on Firefox?

[Jen]

Hi,

I have a bit of a procastination problem (understatement) when it comes to my studies. I need to get rid of all weapons of mass distraction--FACEBOOK, TWITTER, TUMBLR, YOUTUBE, ETC, ETC. How can I do this using Firefox? Or does it have to do with my internet provider company and I have to speak with them?

[biglamp863]

You need someone else to do it using parental control software on your computer. If you do it you will just undo it.
~

[Kasi]

try some smart site blocker app.

[katlyn]

try some smart site blocker app like SentryPC, it can help filter sites easily.
Check monitoring-softwares.com for more info about the program.

[Ríkviðr]

Try using your built-in self control add-on. Works for me.