Easily add custom HTML outside the main container?

I’d action this by adding an additional background video div to the code and positioning fixed. Just need to tweak the z-index to layer the main container and background video.

See demo:
https://jsfiddle.net/t9mznyrq/

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)