Thanks navjotjsingh
Now I can access my rediffmail in Firefox
But I lost my profile because when I restarted FF it said that my profile is being used by another user

I being the only user of this computer and had only one user profile.
No problem again as adviced by you I did backup of bookmarks and sucessfully imported all the book marks. Around 250 in numbers
However I lost all my extensions. Now I am again going to download and install them. Not a big deal considering each of them being few KBs only. I also have to customise FF.
Now I would like to know what happened. Because I do not want face this problem again
Why Firefox and Rediff.com at loggerheads
Thanks once again.