If a minor spelling error (e.g. one letter is wrong or missing) results in something that is not a word, then it's generally accepted with a typo warning. For example, if you write "errpr" instead of "error" -- since "errpr" is not a word, it's considered a typo for "error".
But if you write, say, "excepted" instead of "accepted", that would be rejected because "excepted" is a real word -- just not the correct one in that sentence.
In the end, though, it's you who are responsible for what the sentence says when you press Submit -- double-check your answers to catch spelling errors before submitting them.