Hello Chandan,

Could you kindly provide more information to your question? What happens when you navigate to any website, say google.com?

What is your computer system and Firefox?

The Firefox icon shows up on the taskbar, yes?

You may have corrupt xulstore.json or Localstore.rdf file.

Close Firefox. Open your file browser to this hidden location:

• Mac: *~/Library/Application Support/Firefox/
• Linux: *~/.mozilla/firefox/
• Windows: %AppData%\Mozilla\Firefox\
• *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\

Locate the above files. Then rename or delete them. Restart Firefox.

hi, mozilla just released an update to firefox 49.0.2 that should fix a problem that sound pretty similar to what you've described. you can download this new version from https://www.mozilla.org/en-US/firefox/all/ to see if it works for you too.