Spell checkers still allow typical kinds of errors that you should look out for.
Homonyms. Spell checkers cannot differentiate among words such as affect and effect that sound alike but are spelled differently. Proofread especially carefully for these troublesome homonyms.
Proper nouns. You can add names and other proper nouns to your spell checker’s dictionary so that the spell checker will not flag these words as incorrect, but first be certain you have spelled the names correctly.
Compound words written as two words. Spell checkers will not identify a problem, for example, when nowhere is incorrectly written as no where. When in doubt, check a dictionary.
Typos. The spell checker will not flag heat, even if you meant to type heart. Careful proofreading is still essential.