< screenshot-1.jpg >
Please take a look at the screen shot.
As you can see the ad is only the size of the red box but somehow the system reserved a bigger place for it and when I scroll down until the ad, the ad will follow coming down until it reached the bottom pointed by the "down green arrow". I think this happen only on Firefox, and mobile as well. I'm not sure this had happened in Chrome. Anyway, this only happen recently, I don't think I have seen this before.
I prefer this to go back to how it was. Ads that is fixed and don't follow when I scroll down. This is slowing my site more if I'm not mistaken as I can notice ads are loading slower even not showing up lately.