Don’t trust it. Really. If you are uncomfortable with things like effect/affect, roll/role, or there/their/they’re, you should not trust any spell-check program to do an editor’s work for you. Here’s my no-need-for-further-explanation argument:
While reading a blog post about how best to employ self-editing techniques, one of the sub-headings was “Be Tough.” Another was “Be Fare.”
As in cab fare.
Since “fare” is a word, this went completely unnoticed by the author. Anything I’d just learned in the post was thrown into question–does this person actually know the difference between fair and fare? Is it that this post didn’t matter to the author, and so clicking spell-check was the only “editing” done? Is my precious time not worth a reread?
This author could have published this after ninety readings–who can know? Just remember that a properly spelled word is not always the proper word.
Thank goodness this was only a blog post! Can you imagine having a misspelled tattoo?