If you have several domain names with different extensions and you need all of them to open precisely the same site, you could have the website under one of them and forward the rest. There are a number of ways to redirect one domain to another, like the so-called domain parking. When your web hosting package deal permits it, though, it will be better if you host all of the domains and set up a URL redirect, not a domain redirect. The difference between the two is that while a domain name is hosted, you may still have content for it, set up subdomains, e mail addresses, and so on., while with a parked domain it's not possible to do any of these things. As an example, if you're building localized Internet sites under different country-code Internet domain names, you will be able to work on them, but in the meantime, people shall be redirected to the primary website.