random video playing in background

today i turned on my mac like normal, opened up safari to watch videos online, and this random stuff plays in the background...i recognize it as a video on youtube ive watched before but there is no window to see it or close it nothing is hidden its just sound and it wont stop...ive tried retarting my mac restarting safari and ever time after maybe 10-20 minutes the exact same ad and video plays...i have no clue where its coming from...even tried using a different web browser and it still happens...can anyone help? i cant find anything online and im about ready to throw the thing out the window..