In those screen shots, Safari is consuming unusual amounts of CPU and RAM. It could be flash causing some or most of that. For Flash-related issues:
- Find your Flash version and make sure it's the latest version available. Never install or update Flash from a pop-up on a website. Always go to Adobe's site to get Flash or updates.
- Install ClickToFlash (Safari), Flashblock (Firefox) or FlashBlock (Chrome) to control which Flash content plays on websites.
- Try using the YouTube HTML5 Video Player to watch YouTube videos, when available. (May impact fullscreen viewing. See link for details.) Some have reported better performance with HTML5, while some have reported worse. Try it and find out what works best for you.
I know that was true for a while. I haven't seen much posted about that recently, so I wonder if they've updated it to correct those problems. I had been using the older plug-in version because of those reports, but started using the extension a few months ago. So far, it has behaved quite well. No performance issues at all.