Website Relevance
A good website is determined by the audience it is aimed at. If a site does not fit your needs then it is of no use to you. (Although it may be useful to someone else). Ask yourself the following questions:
Does the site contain information on my topic?
Is the information detailed enough to be useful to me?
Do I understand the content?
You are searching for information on Mount Vesuvius (hint - in Italy).
Which site will not be useful?
Which site includes the dates for all of the eruptions of Ms. Vesuvius?
1)FEMA: Volcanoes - http://www.ready.gov/volcanoes
2)Volcanoes Live - http://www.volcanolive.com/
3)Global Volcanism - http://www.volcano.si.edu/