You will need to install a user script manager extension to install this script.
If You use HTML5 to watch video, sometimes the full screen mode button is missing or not functional. This script fixes this issue by adding allowfullscreen to all iframe tags. Please report, if someone tries to misuse this.
Note: The current version works only on static web sites. If the site generates the video tags dynamically, e.g. as a response to user input, the script will not acknowledge it. Depending on interest, I may consider writing a dynamical version of this script.
The riddle below is just to repel spammers. Everyone else is welcome to mail me. Sorry for the riddle.
public domain by gnblizz
contact me with my user name + "@web.de"