HI,
Try maintenance.
From the Safari Menu Bar, click Safari / Empty Cache. When you are done with that...
from the Safari Menu Bar, click Safari / Reset Safari. Select the top 5 buttons and click Reset.
Mac OS: Web Browser Quits Unexpectedly or Stops Responding
Safari add-ons can cause performance issues or other situations
Try uninstalling and reinstalling a new copy of the Flash Player plugin since it's required for streaming video on YouTube.
Uninstall Flash
Install Flash
Repair disk permissions...
Quit any open applications/programs. Launch Disk Utility. (Applications/Utilities) Select MacintoshHD in the panel on the left, select the FirstAid tab. Click: Repair Disk Permissions. When it's finished from the Menu Bar, Quit Disk Utility and restart your Mac. If you see a long list of "messages" in the permissions window, it's ok. That can be ignored. As long as you see, "Permissions Repair Complete" when it's finished... you're done. Quit Disk Utility and restart your Mac.
Carolyn 🙂