http://www.mozilla.org/en-US/firefox/features/ "Spell Checking: A built-in spell checker works directly in Web pages, like blog posts and email. Save yourself a step and stop worrying about typos."
Now that that's out of the way we need to find out what shape distribution are you trying to fit. Gaussian? Log-normal? Uniform? Rayleigh? Why do you need an analytical function for it anyway? What would you do with it if you had it?
