Thanks, but I'm still concerned :). Beneath I quote the part of the blog I don't understand:

1.in your dev environment add a new http alias for the production environment. You can do this in Admin > Site Settings, but only when logged on as host. For instance, if your dev site runs under http://localhost/dotnetnuke, and your production site will run under http://www.mydomain.com, you should add www.mydomain.com as http alias. Why is this important? Always, when DNN receives the first page request, a lookup against the defined portal aliases is done. If the hostname that is used to request pages from DNN is not found in the list of portal aliases, DNN will redirect to the first available portal alias of the first portal. Quite often this will be your dev environment. A common mistake is to not add the portal alias, and thus be redirected to your devsite when browsing to your production site for the first time

Could you please explain to me what this means? Why can't I just move the website and change the portal-alias afterwards? If necessary at all...