Below please find a link to a very good article regarding the online home value estimator programs.  As numerous consumers are utilizing the various home estimator websites I thought you may be interested in the technology behind the calculations which this article explains.  Relying on these programs for
refinancing or purchasing may be risky at best.

http://finance.yahoo.com/news/the-fuzzy-math-of-home-values-.html

In our market we have found the website reports to be very confusing as the majority of our homes are custom construction which is difficult to value even in the most active markets.  In our current market where “truly” comparable sales are few and far between, providing market valuations for buyers and sellers can be challenging.  As agents, we rely on the old fashion method of manually selecting comparable properties and correlating the market approach with the cost approach to estimate a value.
Shouldyou want an estimate of value for one of the homes you are considering
purchasing, be sure to ask me as I would be pleased to assist.   I
would hate for you to become disappointed after using one of the websites that offer home value estimates for our location