I have found this ('''https://support.mozilla.com/en-US/questions/765179?s=ftp&r=208&as=s''') solution, but I cannot get it to work. When I type '''about:configuration''' into the location bar I get the popup saying: '''''The URL is not valid and cannot be loaded.''''' And the only button available is '''OK '''which does nothing other than close the alert window. This is NOT about updating addons. This message comes up whenever there is Flash content on the page. I DO NOT HAVE FLASH INSTALLED AND I DO NOT WANT TO INSTALL IT. Nor do I want to be irritated hundreds of times per day with this message because I choose NOT to have a SLOW memory hog on my computer. And, yes, this is an old computer and many of the programs are out of date. I don't need information telling me that I should update anything. I just need to get rid of the annoying popup box. The rest I will deal with later.