It's one of your jobs as a college student. Your instructors expect you to be able to determine what sources are accurate, which are biased and which are appropriate for college level research. To determine this you will need to evaluate your sources.
Books, eBooks, and articles from databases in the library have gone through at least two screening processes: someone had to decide that the work was publishable; someone had to decide the work would be of value in the library’s collection.
Even so, not all books and articles are suitable for your research. Books and articles can be biased, so you'll still need to evaluate.
Web sources are a special concern for your instructors because there is usually no screening process. You will be responsible for evaluating the sites you use for credibility.
Even though you now have some great tools from this guide to use to find good quality web sites, it's still up to you to review the ones you find and see if they are suitable for your assignment.
Here's another tool to help you assess your sites: The CRAAP Test for evaluating information (PDF) - is the Web site you are using for your research accurate and reliable or is it a bunch of.........?! This list will help you determine.