Weird glitches on MacBook Air; buggy Safari and Opera, but not Firefox?

Question

Browsers

Good afternoon, such a problem.
There is a 2013 MacBook Air: Core i5 1.3 GHz, 4 GB of RAM.
And under OS X 10.9.5 on it, Safari with Opera opens sites very slowly. Under Win7 on the same machine everything works fine. OS X has been reinstalled, torrents download fine, and strangely, Firefox works fine. And Safari with Opera - no way.

From other oddities - when trying to enter VK issued:
“Cannot pass authorization over a secure connection. Most often this happens when your computer is set to the wrong current date and time. Please check your system date and time settings and restart your browser."
After that, we tried to install Dr. Web - the installation went fine, but it freezes when checking the computer.
But otherwise the computer works fine.

Thanks in advance for your replies.

Answer 1

Maybe it's DNS prefetching? Try turning it off. There may also be something wrong with the DNS... see if everything is fine with the resolution. And also, for example, with mDNSResponder, you can also try to upload, download it.