My ipad 2 ios 7 has a tray at the bottom of the home screen and it makes my wallpaper not to show behind the area it has covered so tell me a solution to remove that tray or make it as bfore it was in ios 6

This is the Dock. It cannot be removed and it cannot be changed.

It is meant to hold your most frequenlty used apps.

iOS 6 also had a dock, it is just flat in iOS 7 instead of 3D like iOS 6.

Try this:

Settings>General>Accessibility>Increase Contrast>Off

You are referring to the Dock. Normally in iOS 7 the Dock is slightly transparent. If your Dock is solid gray you have Increase Contrast turned on. Follow the steps provided by Diavonex to turn it off.