Hi, have a look at this article, in particular, how to set Permissions.

Hope that helps.

HDIVER said

Was having problems with Firefox hanging and script errors. Eventually decided it was Adobe Flash that was doing it. Uninstalled Flash, reset Firefox, reinstalled Flash and requested activation on request; worked great. However, by mistake allowed it to be always activated on newspaper website and now it has gone back to hanging and script errors whenever I access the newspaper stops me accessing anything on any tabs. How do I reset the activation to be' activate on request', without having to reset Firefox?

Thank you so much for the very swift reply. I have done as you suggested and it would appear to have solved my problem. Wish I knew why Adobe Flash suddenly started to behave like that.