There is box or rectangle on the screen moving. How canI get rid of this box or rectangle?

Restart?

If a restart doesn't fix it, do a Safe Boot, Shift at the startup chime. Will take much longer to boot. If upon doing an ordinary boot after a Safe Boot, it returns, it may be the graphics card is going south.

If the box is black and accompanied by speech, press the key combinationcommand-F5to deactivate VoiceOver. If that doesn't work, proceed as follows.

For OS X 10.7: From the menu bar, select

 ▹ System Preferences ▹ Universal Access ▹ Seeing ▹ VoiceOver: Off

For OS X 10.8: Select

 ▹ System Preferences ▹ Accessibility ▹ VoiceOver

and uncheck the box labeled Enable VoiceOver.

Good catch Carnac. 😉