See The Evolution of YouTube's Layout Since It Launched in 2005
It's wild to think that YouTube launched twelve years ago, and next year there will be teenagers living on this planet who have literally grown up with that site. I remember having to visit weird places like ebaumsworld to see "viral" videos online before YouTube came around (anyone else?), and now LaughingSquid has sent me on a trip down memory lane by pointing me to this video from 4096 that traces the evolution of the site's layout through the years: