Astronomy has always attracted people whose main interests diverge from those of scientists -- for instance, astrologers, creationists, UFO zealots, and those who see the face of Elvis in images of Mars. Lots of them take the time to generate Web sites to promote their interests, and to associate advances in relativistic astrophysics and cosmology with their ideas. Beware, therefore, of believing everything you read about the Universe on line; it's easy to find a lot of information that is false. If you're in doubt about a site you've found, please ask us.
You can begin to immunize yourself against these crackpot Web sites by looking at some crackpot-debunking sites maintained by respectable scientists. One such is the Bad Astronomy site, http://www.badastronomy.com. Several prominent cosmology crackpots are debunked by UCLA Prof. Ned Wright, at http://www.astro.ucla.edu/~wright/errors.html . Many resources for the debunking of astrology and other pseudosciences are available in the Astronomical Society of the Pacific Web pages, at http://www.aspsky.org/education/pseudobib.html.
A good example of high-profile falsehood: most people are already used to the idea that not everything shown on television is very likely to be true, but the Fox network outdid even their own past flights of fiction by producing a program (on 2/15/01) called Conspiracy theory: did we really land on the Moon? in an attempt to present some of the more prominently antiscientific crackpots in a favorable light. Corrections to their babblings can be found on the NASA web pages at http://science.nasa.gov/headlines/y2001/ast23feb_2.htm, and in the Bad Astronomy pages under Bad TV at http://www.badastronomy.com/bad/tv/foxapollo.html .