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Firefox seems to rewrite this internally (at least it immediately switches to www.nasa.gov and HTTPLiveHeaders does not show a redirect), but in IE, Chrome and Opera it fails.
Perhaps this should be a Webmaster Gen topic, because it shows the danger of testing your server setup using Firefox. You might think it's good, but you could be depending on Domain Guessing rather than proper server setup.
Oops! Internet Explorer could not find nasa.gov
Did you mean: www.nasa.gov
I typed nasa.gov in and it redirected me and loaded the www version. I guess they caught on fast? Or did my browser (Firefox 12) "fix" it for me?
My gut tells me there's just a checkbox on a managed dedicated server control panel for " www" that nobody checked and is unchecked by default.