It's not easy to determine whether information on the Internet is legitimate or correct. There is a lot of inaccurate and deceitful information on web sites, in e-mails, and even in news and newsgroups. False information can occur from mistakes or oversights, but the biggest problem is information that is out of date.
Malicious information also exists on the web. Some examples are: products that don't really exist, fabricated news stories, misleading statistics or financial reports, false virus alerts, pyramid schemes, etc. Unsolicited email (SPAM) is the primary culprit in the dissemination of malicious information today. Many SPAM emails are actually SCAMS.
My best advice on the SPAM situation is DO NOT RESPOND (either with a reply or by clicking a link or by opening an attachment) to any email you get that is from a company or person that you have never heard of. I recommend liberal use of the DELETE key and learning to use the filters (or Rules) that come with your email program. Also beware of suspicious emails from companies you do know, especially if they do not use your real name. These may be "Phishing" scams which attempt to get you to reveal personal information which could be used for identity fraud.