The Internet is a jungle of information. Every second millions of thoughts, ideas, and knowledge is exchanged. The Internet is a powerful research tool with limitless potential however the Internet can also be very counter productive to your research. It is really easy to lose track of what's credible, what is current, or even what is true and false. When viewing a web page you should ask yourself a series of questions organized by Who, Where, and What.
Ask yourself, who is the author of the piece? Is he the original source of this information? Does the author ever specify his or her education, expertise, experience, or position on the subject matter? Given your answers to the first questions, do you feel that this person is qualified to write on this topic? If no, then you may want to search elsewhere for a stronger source.
Inspect the website and answer what institution (company, organization, government, academy) or Internet Provider supports this information? If this site is from a commercial Internet provider, does the author appear to have any affiliation with a larger institution? If yes, then is this institution a national, local, or international institution? What is the author's affiliation with this particular institution? Does this institution show any signs of filter any kind of information? If you cannot identify where the information or author is from or if you can identify the origins but still don't find the institution credible, then you may want to consider searching elsewhere.
If you are unsure about the top level domain (or extensions such as name.COM, name.NET, name.GOV, etc) you should look it up at IANA's Rootzone Database.
Finally you want to look at the information itself. Can you find when the document was created or last updated? Do you feel that the information is current? What is the objective of the document? Is it trying to inform, explain, persuade, instruct, etc. ?
Given all the information you determined from the above questions, is this Internet site an appropriate source of information for your topic? Would you have any reservations in telling someone else to use this information? Would you make any disclaimers in using this information?