I haven't a clue where this is from, so I'm just going to provide a visual description. This is an animated gif of a long-haired guy opening a door. After seeing what is on the other side, he recoils in horror / shock and pulls a funny facial expression. The man in question has long curly brown hair and he is wearing clothes that would indicate that he is from the 70s. This is a classic reaction gif and I've seen it around a thousand times.
Edit: After doing some searching, I've found that this gif is from Italian Spiderman.