It depends on the type of web site. Some are opinionated and ideological.
However, based on the assumption that your question is about the web site of a newspaper that is also printed, surely the credibility must be the same, as it is the same publishing company.
This quote can be found only in the movie. It can be heard in the third movie, and is told by the headmaster. I just checked the book, and it doesn't appear there.
