The page http://stackoverflow.com/users/122299/ result in Firefox saying that
Firefox has detected that the server is redirecting the request for this address in a way that will never complete.
Indeed, some investigation shows the page to redirect to itself, while my page, http://stackoverflow.com/users/126214/ redirects to http://stackoverflow.com/users/126214/lennart-regebro
Thus I suspect that this user, who has no ascii character in his name, has triggered a small bug. :)
User Details on http://data.stackexchange.com