Hm, guess it is the ads. As many of them are Adobe Flash, they can do MANY things besides a simple redirect to another page.
Besides the easier ad block plugin option, you could go after the ad domains and neutralize 'em via a hosts file. Here's how a line in my hosts file appeared:
23.193.234.144 pagead2.googlesyndication.com www.google-analytics.com
What happens is, those domains are forced to resolve to another IP address, I used Microsoft's. So any website you go to that uses them, gets nothing from whatever JavaScript ad-serving code is linked. A not found message in principle, so yeah, it has the effect of neutralizing it all with no need for plugins in your browser.
I had to keep this for Photobucket cause they pack a punch with all the ad serving and the page loading is God awfully slow just to upload an image, wasting 5 minutes to finally get to do it. You can use Google's Search IP address here as it's less likely to change as often. The entry in the file looks like this:
#Photobucket Block
216.58.216.196 b.photobucket.com rtax.criteo.com view.atdmt.com b.scorecardresearch.com
216.58.216.196 www35.glam.com loadus.exelator.com secure-us.imrworldwide.com
Browsers all have to be restarted, but a reboot is not necessary for changes to take effect. I dunno where this etc/hosts file or something similar would be on a Mac machine though. You'd have to look that up. One other drawback is if Google or MS change those IPs and they go bad, page loads will be slow waiting around for a server response. You have to remember you did this and do a "ping
www.google.com" command to get the latest IP address and update the file on occasion.