The stop and refresh buttons have been combined into one button, located on the right edge of the URL text box.

To locate this button, find the refresh button on the right edge first. The icon should have the same graphic as previous versions.

The moment you hit Return to load a web address, this button will change to stop.

Sorry but this is wrong answer. In firefox not ability to stop loading a page. I send two screen shots for that. This is Bulgarian sait for verifying payment for our national energy firm. In first screenshot you see how script is loading. In center of screen is animation gif in Bulgarian - in English this say 'Loading , please wait.' After pressing the reload buton (that must be a combination with strop and reload), I receive second screenshot - in english this buttons say "Reload" and "Discard" after pressing Discard script continue to loading. Not stoping forever. Only close a tab. In Opera this actually stop a script but again bad decision with combination of two functions. I'm very angry. I'm developer from 20 years, and dont understand like decisions.

About box of Firefox say me a version 9.0.1. OS is Windows 2000 and I will change this to FREE BSD forever.

I'm having trouble stopping page refresh, too. huffingtonpost.com nowadays keeps updating things on its home page even while I'm trying to read them. I cannot get the refresh button to change into a stop button to pause page updates. Is there a workaround?

Some websites use a script or meta tag to update the page automatically at regular intervals.
You can't use the Stop button to prevent that in such a case.

You can use NoScript to block scripts if that method is used.