Try this:

Press F10 or press and release Alt to display the menu bar

View > Toolbars > Customize...

Check the box labeled "Use Small Icons" and click Done

Does it work?

Maximize the window.

i dont know what exactly happened but when i restarted ff it opened the way i wanted it...maybe a new addon was interfering.. my ff was maximised when i took that screenshot... i dont think the small icons option is affecting it.. but the other option is toggling the feature...

Thanks both of you for replying so fast and suggesting the solutions.

hey, sorry but the problem seems to have returned this time i started my firefox. i tried everything but doesn't work. thanks.

Maybe you can be more specific about which part isn't working.

Small should change your location bar to look like the other picture. Does that part work?

When you maximize the window, the page tabs should slide up next to the orange button. Does that part work?

Firefox might not remember whether you used it maximized in a previous session. However, if it forgets all of your toolbar customizations that can indicate a corrupted file.

the small thing works just fine.. what i want is the tabs to be placed next to the orange button.. its working now but very occasionally when i start ff it appears below separately. (even when maximized). the other toolbar customizations are just fine.. Thanks for you interest..