Firefox doesn't use the concept of trusted websites.<br /> As long as the standard settings are used everything should work fine. What kind of problem do you have that you want to trust a thread? Did you make changes to the cookie settings? *Tools > Options > Privacy > Firefox will: "Use custom settings for history" Can you attach a screenshot if it is a problem with displaying content? *http://en.wikipedia.org/wiki/Screenshot *https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem Use a compressed image type like PNG or JPG to save the screenshot.