Facebook and Youtube says update your browser.

Hello. I am running OS X Yosemite on my late 2011 MacBook Pro. I have latest Safari (10.1.2) Installed and Facebook still says: For a better Facebook experience, update your browser. I also get similar message on Youtube and when I type sth in the search box, no dropdown menu appears.

Is this a Yosemite Issue? Because friend doesn't have that problem and he is running even older system (Mavericks I think). Another friend on Yosemite with a newer MB Pro, also without problems.

I did make a clean Install of Lion few weeks ago, then upgraded to Yosemite, could this be the issue? If, then why? The system works great and this is the only issue I've been having.

It doesn't bother me that much, but I'd still like to know what could this be.

Thank you for answers!