Public service announcement: everyday vs. every day
everyday: An adjective that means something is normal or typical. (Merriam-Webster) For example, "everyday low prices," or "everyday average guy."
every day: A set of days when something might occur, that is, all of them, generally used as an adverb. For example, "We have low prices every day," or "Every day, I'm an average guy."
Hint for using adverbs: you need a verb before you can add to it.
Unfortunately, my dictionary doesn't have "every day" in it because it's just a normal combination of two words. But if you look up "everyday," you will find that things like "low prices everyday" or "people do this everyday" don't work.
See also my hybrid personality/vocabulary quiz.