This function is very limited. It was designed as an accessibility feature to help prevent screen reader software from getting confused by changes of context. It is woefully incomplete as a possible security tool, since there are many ways to redirect and the feature only addresses a few of them. And of course there is no way to make site-based exceptions. Hopefully there is an add-on which does what you need.

jendrew said

4) Rather I navigate to preferences, security and add the exception in manually under popup. I think I have done it correctly.

The Exceptions dialog on the Security panel of Preferences is not related to popups or redirects, it is related to whether websites can install add-ons to your Firefox. I do not recommend manually adding exceptions for this. Instead, Firefox will drop-down a message from the address bar when a site wants to install an add-on and then you can give permission that way.

The Exceptions dialog on the Content panel of Preferences is for pop-up windows, but unfortunately this doesn't help with the redirect warning.

Thankyou jscher2000 for your helpful information.

I unchecked it as you say,

  It was designed as an accessibility feature