I have recently been getting the "Firefox prevented this page from automatically redirecting to another page" warning when viewing pages on the site. Clicking "allow" gets rid of it for some time.
Is it connected to a pop-up that the site generated some time ago ?
I am using Firefox 19.0 beta, Microsoft security essentials, Superantispyware, Malwarebytes, and up to date Windows 7 pro.
I agree, it can be a useful feature. One of the search engines for multiple Craigslist's required that feature to be active. Apparently, Craigslist (a free listing service for individuals in the US) didn't want users to be able to do that.
Go to Tools>Options>Advanced>Accessibility and check what your setting is for re-directs.