Scroll to the bottom of any article on The New York Times webpage and a popup window slides in at the right bottom. It shows one of many articles NYTimes wants you to read. I find such dynamic behaviour on long-form content webpages highly irritating.
To stop this popup, add this to your Adblock Plus addon:
Tried with: Adblock Plus 1.3.3 and Firefox 4.0 on Windows 7