Spelling and grammar checker can be very helpful, but they do have certain problems.  They:

• Do not catch shifts in point of view, verb tense, and mood
• Often ignore the misuse of adjectives and adverbs (e.g. “could have been handled more professional [should be professionally
• Catch, but more often don’t, misused semicolons and run-on sentences
• Will not tell you how to spell words not listed in its dictionary, catch words commonly confused (e.g. affect/effect), homophones (e.g. son/sun) or typos (our and out are only one space apart on the keyboard)
• Miss words that should be capitalized in certain contexts (e.g. Dad/dad)
• Don’t consistently flag slang and informal language