Workspaces keep switching while i have an app fullscreen.

I just bought a Macbook Air(13.3") and i am loving it for the most part. But when i have Safari in full screen and am watching a video in fullscreen, every few seconds in the video, the workspaces will change back to Desktop 1. I cant seem to figure out why this is. Its just keeps changing, no notifications or anything are popping up, it just changes, then i have to go back to the other workspace with the 4 finger gesture. Then after a few seconds it does it again. This is very annoying.