In case you have a lot of domains with different extensions and you need all of them to open exactly the same site, you may have the website under one of them and forward all the rest. There are a number of ways to redirect one domain name to another, like the so-called domain parking. If your web hosting package allows it, though, it shall be better if you host each of the domains and create a URL redirect, not a domain redirect. The difference between the two is that while a domain is hosted, you can still have content for it, set up subdomains, e mail addresses, and so on., while with a parked domain you can't do any of these things. As an illustration, if you are building localized Internet sites under different country-code domains, you'll be able to work on them, but at the same time, people shall be forwarded to the primary Internet site.