You need to critically evaluate ALL information sources, whether from the web, in print, your professor, or the library (this can be done at differing levels; you generally want to evaluate at a deeper level items you find on the open web). Ideally you want to make sure you are finding literature that represents a variety of viable (and potentially conflicting) perspectives on your topic. You also need to critically evaluate each piece of information you intend to use in your research for:
Evaluation techniques: