One of the most common mistakes I see is the misuse of everyday for every day. The former form is an adjective, meaning “commonplace” or “ordinary,” and the latter form is an adverb or a noun, meaning “each day.” Here are a few examples:
“Every day [each day] is special.”
“Bob disliked the grind of everyday [commonplace] life.”
“Johnny gives money to Billy every day [each day].”
