Cite your Sources!
Document the location of clipart and photos that have been copied from other websites. Add the web address, for example: http://www.teacherfiles.com. Remember music included in a movie must be copyright free. Be sure you own what you attach to your website. This especially includes classroom curriculum resources.
There are photo resources available in which images provided are considered public domain. No attribution needs to be provided. As a rule, always check the copyright details and permissions of images and sources used that aren't your own.