Is that a page you were trying to open, or did the page you wanted redirect to that error, or did the tab just appear unbidden like a popup? What's the frequency of appearance?

Have you checked for the addition of any unknown extensions on the Add-ons page? Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then cast a critical eye over the list on the left. As a test, if you won't need something for the next 24 hours, try disabling it.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Does that change the behavior?

Has your external security software updated recently?

yes it is the site i was looking to go to, was not a redirect was a clean link, and had no adblocker or anything turned on (was the 1st thing i tried). and being the dumbass that i am it was my dns agent causing the problem (the 1 dam place i didnt check and forgot about cos its new) thanx for your help and apoligies for the time wasting