i have closed the address bar , navigation bar & others & unable to open it... what should i do???

I have done the same thing, inadvertently closed the address bar.

How can I bring it back?

In Firefox 3.6 on Windows you can hide the menu bar via "View > Toolbars" or via the right click context menu on a toolbar. Press and hold the Alt key down to bring up the menu bar. Go to "View > Toolbars" or right-click the menu bar or press Alt+V T to select which toolbars to show or hide.

See also Restore the Menu bar in Firefox