Is it permissible to use anything you find on the Internet in your presentation?

What will be an ideal response?

Anything on the Internet should be considered copyrighted unless the site specifically says it is in the public domain. If it is public domain, the author is giving everyone the right to freely reproduce and distribute the material, thereby making the work owned by the public at large. Facts themselves are not covered by copyright. Images are protected unless the owner gives his or her permission for downloading.