my mac book blocked youtube website please help

Likely because you do not have the latest version of Flash install.

You can try download the latest version of Flash or configure Safari so that HTML5 and not Flash is used. For that see:

https://www.youtube.com/html5

To update go to System Preferences>Flash Player>Update and update it there

Also go to Safari>Preferences>Extensions

Also, make sure Flash is enabled

https://helpx.adobe.com/flash-player/kb/enabling-flash-player-safari.html