how can i fix this problem,please help

Have you changed theme somehow by mistake? Is the top title-bar of a window brown or some other colour? Do you still have the grey panels at the top and bottom of the Ubuntu screen? Can you click on the firefox button on the taskbar and does that minimise the firefox window? Another work-around might be to use the second desktop down by the waste-bin (bottom-right) - try your mouse-wheel down there :)

If you are using compiz,

Please open Compiz setting manager from menu System-> Preferences-> CompizConfig Settings Manager

In the Effects section, please make sure the Windows Decorator is ticked. Then restart compiz.

Hope this helps

my firefox problem solved,
i pressed F11 and then fullscreen view was displayed,
after i restarted my system,firefox page showed no problem,the oage includes minimize,close and fullscreen button at the upper right corner.

But minimiz problem not solved,
i can't access minimized pages by mouse as they are not visible at bottom panel.

i uploaded my screenshot at flickr with a title"Screenshot of my ubuntu minimizing problem"
this screenshot will give a clear idea about my problem

Can you please link to the picture you uploaded?

http://www.flickr.com/search/?q=Screenshot+of+my+ubuntu+minimizing+problem

I think I didn't fully get the problem.
As far as I can see from the screenshot, there *is* a minimize button.

As your second issue, you raise that you "can't access minimized pages". By "pages" you mean windows like Firefox or a gnome-terminal?
Your screenshot doesn't even show the bottom panel, so it doesn't reflect your issue at all.

Can you un-confuse me please ;-)

Thanks to Muelli, yes i meant window when i said page.
i've uploaded new screenshot at facebook in an album named "My ubuntu problem"
find me in facebook by the name Minhajul Anwar / <email address hidden>

I'm sorry. I will definitely *not* go to "facebook"s website and search for your profile. If you want to share photos, please find a way which allows to distribute direct links for everyone to see. I think http://imageshack.us offers such a service.
I am offering my helf here, but I am asking you to be cooperative and I expect you to be able to write up your problem in a comprehensible way. I couldn't find that up to now.

So I am asking you once again: Please provide a clear description of your problem, including what you did, what happened and what you expected instead. Also, any further information, such as images, must be available with a click of a button. The more *you* increase the barrier to get to the information necessary to fix your problem, the *less* are the people willing to help you.

Thanks to everyone specially to Muelli,i am really sorry if i bothered you and i will try to be more cooperative from now.
 i've solved the problem.
After uploading photo screenshot in facebook, one of my facebook friend wrote me that it is a simple problem and as i am new ubuntu user so i could not solved it by myself.
he said to right click in the bottom panel and select the item named "Window list".
this solved my problem.
Thank you for your valuable advice.