Everything on the Internet is considered common knowledge - WRONG! Unless it meets the criteria of common knowledge, you must cite your sources, whether found on the Internet or in print.
Information found in an encyclopedia is considered common knowledge - WRONG! Encyclopedias contain lots of information, some of which is common knowledge and some of which is not.
Facts found in newspaper articles are considered common knowledge - WRONG! Newspaper article do contain facts that may be consided common knowledge, but not everything included in a newspaper article is common knowledge.
When in doubt, check with your instructor or cite the information.