magento admin log in issue

It took me awhile to figure out an issue regarding the backend part of magento. I've installed magento 1.3 on a linux ubuntu 8.10 environment. Everything went nice until the admin log in part. Well, nothing happend after logging in the admin panel. I've tried lower versions of the magento installer but without any success... I tried to read some forums and saw the answer. It was about the naming of the host. It would not work if a dot is not present. Such a very simple issue that i've learned the hard way. For example, http://magento will have an issue, so add something like http://magento.linux etc on the name for it to work properly.