What can cause a persistent “Reload the page to get source for” error in firebug?

Question

I\'m trying to debug the javascript of a specific page, and I keep seeing

Reload the page to get source for page.htm in Firebug.

On Chrome, I\'m

Answer 1

It may also be due to "302 Moved Temporarily" error. You can check it in firebug's Net tab.