Hello atul61, firefox usually should open in the last closed state, if it is in full screen mode when you close it, then when you restart it, restart in full screen mode.

see if you like : https://addons.mozilla.org/en-us/firefox/addon/FF_Fullscreen/

thank you

But there is no other way to open that in full screen mode?

can i change something in about:config so that it will work ??

This setting is stored in the localstore.rdf file in the Firefox profile folder.

• http://kb.mozillazine.org/localstore.rdf

You you can check this file to see if sizemode="fullscreen" appears under the browser.xul#main-window heading.

If have this section when the normal dimensions are 1024x720.

<RDF:Description RDF:about="chrome://browser/content/browser.xul#main-window"
     height="720"
     width="1024"
     screenX="323"
     screenY="90"
     sizemode="fullscreen" />