I used to think that "everyday" was always one word, but I soon learned that I was wrong.
"Every day" as two words can literally mean "each day." In the sentence, I feed my dog, Payton every day, can also mean that I feed my dog, Payton each day.
After learning that "every day" means each day, I soon wondered what "everyday" meant. "Everyday" is an adjective that means commonplace, ordinary, or normal and is used in front of a noun. (http://www.elearnenglishlanguage.com/difficulties/everyday.html). In the sentence, You shouldn't wear an everyday outfit to the wedding, "everyday" is describing the outfit.