Hello
I am new user.Compiz is not working in kde 4.8.4.
plz tell me how compiz works in kde.

Kde doesn't normally use compiz. The native window manager for kde, kwin, is a compositing window manager making the use of the compiz window manager unnecessary. Reading between the lines, I'm guessing you can't get the normal kwin compositing desktop effects to work. You can activate the desktop effects in kde by going to System Settings>Desktop Effects. If the activate box is grayed out, it's probably because your graphics card is incapable of running a compositing window manager or you need a proprietary driver for your graphics card to enable that capability.

can i use compiz by installing Smaragd (Emerald for KDE) if yes then how can i download this?

You should be able to. Furthermore, install fusion-icon and set it as a startup item -- and you should be able to easily toggle between compiz and kwin.

Thanks...