Adblock Plus {web link} Blocks annoying video ads on YouTube, Facebook ads, banners and much more. Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).

Adblock Plus Pop-up Addon {web link} Adblock Plus Pop-up Addon extends the blocking functionality of Adblock Plus to those annoying pop-up windows that open on mouse clicks and other user actions.

Forum; Adblock Plus Homepage {web link}

I have Adblock Plus. I want something that stops sites with a word in it.

Go to the Mozilla Add-ons Web Page {web link} (There’s a lot of good stuff here) and search for what you want.

There are 'block site' add-ons available.

Are you referring to your email??

Some webmail sites allow you to create filters, and possibly those filters could delete unwanted spam from your spam folder. However, unless you are busy reading your spam folder, it might not be worth the effort to research and implement that.