If you have Adblock installed, go to its settings and add the following filter: asset.pagefair.com (that is where it's coming from, at least on here) and the problem will go away.
Whatever that site is and whatever it's being used for on here, it's infected with something (i.e. Flash is NOT out of date; I have the latest versions and everything I've read on the Net indicates that it's a fake and possibly designed to get you to click on the button to infect your computer somehow. I doubt it does anything to Macs, regardless, but can lock up the web site by not allowing anything else to load.