Disable Shockwave Flash in Firefox:
  1. In Firefox click Open Menu which looks like three gray lines on the upper right corner.
  2. Click on Add-Ons *
  3. Look for Shockwave Flash and on the drop-down next to it, switch it to Never Activate.
*If you do not see "Add-Ons" in your menu in Firefox, pressing Ctrl + Shift + A will open the Add-ons menu