Let me begin by bursting a bubble or two...just because it's "printed" online doesn't mean it is either accurate or correct!

Most data found online is in a pretty plain format with no frills, although some has more information than others. As with any form of offline research, you have to approach information obtained online as a guide only, not as a source of primary information. Always look for a source citation showing where the information originated. Even if the site lists a source, the question of evaluating the quality of the data still remains! You have to examine the information and the source to determine whether you need to investigate further.

When viewing data online which looks like it's relevant to your research, you have to ask yourself--is the source of the information cited somewhere? If the data is part of a project, do the volunteers list which resources they used to transcribe the information? Take a good look at the data and how it relates to your information--are there inconsistencies? Does the data make sense? If there are contradictions in information, weigh the evidence. Which piece of information seems most reasonable? Never accept any information as valid until you can verify it, or at the very least, have a citation for the data's source in your sweaty little hand (my hands always get sweaty when I find new data!).