The game starts, then first I press enter and a black screen appears. And nothing happens. After restarting the page (F5) I get "Your browser does not support WebGL".
You have to restart your browser to get it working again. Not with other games.
Finally got what the error is. It seems that your browser may not support the version of WebGL used to export this game. That, or it could be that this is the first game that was made with Unity that you tried to play from the browser, and your browser doesn't suport WebGL at all.
