Basically your browser "forgot" what it's been doing.
I've been having this trouble a lot lately, every time I log into my bank or Facebook I get an extra security alert--turns out it is because my ISP is moving around my IP address, sometimes I'm in Kent, Sometimes an ISP in Seatac, Sometimes in Burlington (I don't think I've ever even been to Burlington).
Cache and cookies are memory (check your security settings on your browser and firewall and see how often they're cleared)
Items like I described above with a moving IP can be your router (if it grants random IP addresses, or your ISP, if it assigns addresses). I don't know how to secure them, but I can recommend a great computer guy who could help out (he works remotely on machines) and can set up all those security settings for you. |
