One of the most annoying things on Facebook are videos that start playing automatically while you're scrolling down the page. I went clicking around in the settings to see if there was an option to disable this and yes there is one.
Go to the settings menu by clicking on the upside-down triangle, usually last symbol over to the right and click on Settings & Privacy.
Then Settings.
Then down the left-hand menu, click on Videos.
In the Auto-Play Videos section, it's probably set to Default, which is On. Just click on it and in the drop-down menu just click on Off.
