Many point-and-shoot and digicam cameras don't have threads on the front of their lenses.
Therefore, you can't screw on filters.
Your camera manufacturer may have a lens adapter for your camera.
Check your instruction manual under Accessories or the website of the manufacturer.
The manufacturers below may have an adapter for your camera.
Cokin makes several lens adapters.
The Digi Shoe Holder A300 attaches to the tripod socket on the bottom of your camera, and uses Cokin A-series filters.
Digi Shoe Holder A300
The Cokin B400AC-M Digi Magnetic Holder attaches with adhesive, and uses A-series filter holder filters.
The Cokin Universal Ring P499 attaches with set screws, and accepts a P-series filter holder.
LensMateOnline For Canon