I think it was around 1997 when I first thought, "gee, it would be great if when I made an obvious typo in a URL, the browser would cleverly fix it for me." I'm glad to see that progress marches apace: URL Fixer
is an add-on for Firefox by Netscape developer Chris Finke that, a decade later, solves this problem, or at least takes a good stab at it. When you make an obvious typo--like using a comma in place of a dot, or typing ".cmo" instead of ".com"--when entering a URL in the address bar, URL Fixer will automatically correct it (or, optionally, prompt you first). OpenDNS
has similar functionality, but in case you don't want to futz with your DNS settings, URL fixer is a solid alternative.