У вашего броузера проблема в совместимости с HTML5
First video to youtube ever so hope it plays alright!
This video is about how to create Mac OS Mojave bootable USB.
Here is the code you copy and paste into terminal:
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/Free
The link to follow the steps on Apples website:
https://support.apple.com/en-us/HT201372