I'm not an admin.
I run Google Chrome with adblock. There's no ad. SO there's a fix - or check to see if Firefox has an adblock extension.
I opened Firefox to see if I could replicate the problem. I see the ad. However, it didn't block any of the post.
If I resize the window, the ad stays a fixed size and text from your post adjusts around the ad.
Are you running a low screen resolution, maybe?