Correct spelling, explanation: this phrase is created from two words and we do not combine them into one. Preposition in and noun front as an idiom are always written separately. This is why infront is a mistake and the correct form is in front.

Definition of in front:
idiom, in a forward place
Jack is in front, let’s go and talk to him.
And there, in front, the principal is sitting.

Incorrect spelling, explanation: we don’t spell this phrase together as these are two separate words creating an idiom. Therefore infront is a misspelling; there should be a space between preposition in and the noun front. The correct form is in front.