Magic Forums

I use Firefox mainly for SoM and have been for a while now. It was only in the past day or two that I started getting ads popping up from the right side and bottom of the screen. This does not happen on any other site I use and it does not happen in Chrome or Internet Explorer. I'm fairly sure this was not an update for Firefox as I've double checked all of my add-ons and nothing was changed recently. What confuses me is that only happens on one site and one browser and I have no idea why it's happening or how to get rid of it (Gods know I would love to, as it is more annoying than anything).
Any help would be greatly appreciated. Please and thank you.