If a page is still loading, there is a STOP button in place of the RELOAD button.

In addition to the above:

Firefox 4 uses a combined Stop/Reload/Go button that is positioned at the right end of the location bar.
During the page load process it shows as a Stop button and after the loading has finished the button is changed to a Reload button.
If you type in the location bar then that button becomes a Go button.
You can middle-click that Reload button to duplicate the current tab to a new tab.

Lol, I love how that's the answer you used on that other question about the back button… XD And also your answer is basically a really lengthy version of my answer. XD

No that is exactly

No, that is exactly the problem... the arrow keeps spinning indicating that the page is continuing to load even after it appears to have completed, and no stop button appears.

If it is spinning something associated with the web page is still loading.