I have windows pro 7 desktop.Downloaded latest version of Firefox which was working fine then AOL malware browser hijacker got onto Firefox ,so I must have inadvertently downloaded some software where that was included.I got rid of that and deleted then reloaded Firefox and that is where trouble started.Now any of the major site google,YouTube,or just about any site has" This Connection is Untrusted" dialogue box appears. On Google Chrome and IE11 all works perfectly Firefox has the best functionality and add on extensions when it is working howsoever for productivity I need a stable browser where a computer science degree is not required to get it to work properly and reliably is there a simple remedy to fix the problem? I have read through the other advice offered and tried delete cert8.db that did not fix anything Anyway I like the idea of group collaboration as an independent alternative to Larger corporations however that will only work if the product is stable,reliable and user friendly You have my appreciation in advance for assisting me with this problem Thank you