Why does playing videos in browser makes them hang it?

[AC Question]

Hello, I'm using a certain website for watching videos, which seems to be using the system's player. Sadly it's very unstable. It's unable to play the video in many cases and sometimes it even makes the entire browser hang/not respond. It's happening mostly on Chrome but Firefox, Dolphin and other browsers are having these issues as well. I'm running on the latest CM 12.1 nightly on Nexus 5. Any suggestions?