Most Web sites have a .com domain name. Sometimes it's better to restrict your searches to other domains, such as .edu or .net.

One great example of this is if you are looking for information about textbooks, but you didn't want to buy a textbook. An unrestricted Google search would mostly yield results from Web sites selling textbooks. One way to avoid this problem is to restrict your search to American universities. To do this, you'd search for:

site:edu textbook

You can use this to restrict searches are to US government sites site:gov, or only specific countries site:uk.

You can combine the site: syntax with many other types of Google syntax