The references you use in a paper are there to support your assertions and arguments. Therefore, you should use high quality references whenever possible. An outstanding example of a high quality reference would be a peer reviewed academic journal. This is because the material is frequently based on primary research and then vetted by a blind review of peer academics. An example of a poor source would be a textbook or website. In the former case, textbooks are usually not peer reviewed. In the latter case, anyone can post anything on the web without any scrutiny.
For an example of a peer reviewed journal, see Cabell’s research database of academic journals at http://www.cabells.com/index.aspx.
For an excellent site on how to evaluate online sources for academic papers, including how to find peer reviewed sources with databases such as EbscoHost, see http://jerz.setonhill.edu/writing/academic/sources/sources.htm
Also, please be sure to visit http://zapatopi.net/treeoctopus/ and help save the endangered Pacific Northwest tree octopus! Remember: Anyone can post anything on the Web!