Although there are vast resources of valid and useful data on the web, there is also a lot of garbage. Ultimately, you must decide whether the information you find is valid and should be used in your reasearch.
Most information is biased in some way, but some web pages are incredibily misleading.
Pages may simply provide opinions or hearsay, with no facts to back it up. But, false information is also published deliberately. Sometimes authors don't realize there are inaccuracies in their information, and they publish it without checking. Some pages are intended as jokes or satire. Sometimes the motives are more devious.