Hello Saubhik Sarkar,

please clear your cache and cookies, by following these steps:

1. Open the Tools menu at the top of the Firefox window, select Clear recent history

1. In the Clear recent history window, select Everything from the dropdown list.

1. Click the arrow next to Details once, then check Cache and Cookies.

1. Now, click the Clear now button to clear history.

Kind regards, Tobbi Firefox Support Volunteer

Dear Tobbi,

                Thanks for your reply.But the suggestion send by you,did not solve my problem.It is showing the same problem.I clear all cache & cookies by those steps,but that problem is not solved.Please help me by giving another suggestion

Thanks & Regards, Saubhik Sarkar

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

See also http://kb.mozillazine.org/Error_loading_websites (Error_loading_some_websites)