As the author of the WWW FAQ, I regularly answer questions about the workings of the Web. If a question is frequently asked, I simply add an article to the FAQ. But sometimes a question is more detailed, more in-depth— not really a FAQ, but still of interest to others. You'll find those questions, with my answers, here in Innards along with commentary on other web-technology-related topics.

Q. Please tell me the difference between the names www.example.com and www-example.com. Thank you.

A. There is a BIG difference!

The dot just looks for a sub-domain called www within the example.com domain. The owners of the example.com domain can set up addresses for any number of different hostnames within the example.com domain. Among other reasons, this is useful because companies often have different web sites for different purposes.

The hyphen (-), on the other hand, is part of the domain name itself. www-example.com and example.com are completely separate domains which could be registered by separate people. And that is very bad news if the one is trying to impersonate the other.

You should never trust a web site with a name like www-example.com to be the same company as the "real" example.com.