what is a credible website?

Answer 1

http://lib.nmsu.edu/instruction/eval.html
Read the Criteria section here.

http://hanlib.sou.edu/searchtools/evaluate.html
And this, too.

Answer 2

These sites explain how to evaluate websites.

http://mason.gmu.edu/~montecin/web-eval-sites.htm

http://credibility.stanford.edu/guidelines/index.html