Support Forums

How accurate are these kind of websites?

How do they calculate how much a website is worth?

I wouldn't use them, they don't take a lot of things into account.

I don't think that they're accurate, they calculate estimate value that your site could be worth.
They scan your site and other sites that are linking to your, gather information about visits to your site, and few more things.
I don't know much about that, but you can check this site to see what information can be found about SF.
http://www.alexa.com/siteinfo/supportforums.net

I'm not sure how accurate they are, but the websites get their values from the amount of traffic.