Currently Being ModeratedDec 17, 2013 5:39 PM (in response to Bob Pal)
AV software is not really necessary as the OSX is all firewall. I have found that things like Norton slow the system considerably so have always given them a wide berth.
What I find with my system running slow is that I usually have a whole bunch of apps still running, so try quitting everything but the browsers and see what that gets. Also, there are a lot of Flash-enabled websites that just run clunky no matter what. In fact, they seem to be increasing out there..
I have a MacPro and USAToday's site stops my browser - all of them actually - in their tracks. You may be experiencing Flash-related security issues - part of why Apple and Adobe got a bit spiky with each other a few years back, is that Flash tries to grab onto too many system resources.
Go to the adobe site directly and get the latest Flash update (11.9) and see if that works.
Also, some of the Chrome plug-ins like Adblock and NotScript go a long way to trimming out the junk that afflicts the more mainstream poorly-coded commercial websites.