It is challenging to determine whether information from the Web is credible and can be trusted. Is it factual? Biased? Relevant to your topic?
Here is a handy acronym to help you determine if a source may be CRAP.
Objectivity is assessing to what degree does an author's bias affect how and what information is presented. A lack of objectivity can be problematic as the author may misrepresent/misinterpret information. An author's bias may also show itself in an omission of information of relevant or important information. Bias does not necessarily invalidate an author's work, but it should alert you that a counterargument source may need to be acquired to balance your research. Below are some questions to ask when determining the level of a source's objectivity or bias.
Below is a graph which attempts to chart the type and degree of bias found in many major news outlets.