Why can't I log into my accounts and why is the verbage "The connection was reset" displayed when I try to pull something up from the internet?

Why does a box pop up staying The connection was reset. The connection to the server was reset while the page was loading. Gives 3 reasons: 1) The site could be temporarily unavailable or too busy. Try again in a few moments. 2) If you are unable to load any pages, check your computer's network connection. 3) If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web. And I am not able to log in to my online banking account. Why? == URL of affected sites == http://