AVOID these guys. Notice they are AdBlockER with "ER", not AdBlock!! From some shady folks in Bulgaria (the real AdBlock is German I believe).

It's a Free trial, but on expiration it continues to add a floating shield icon to many Firefox pages at bottom right, which prompts you to upgrade and pay.

Remove it with Firefox menu, remove it with Control Panel programs, it's still there. Directory "C:\Program Files\AdBlocker Ultimate" cannot be deleted, because there is a process, visible in TaskManager. Reboot the PC. Process gone, directory can be renamed.

But still, when I open my email client (fastmail) in Firefox, it still hangs for a long internet-timeout, saying "Connecting to self.adblockultimate.net"