You can change the host name of your portal. This must be done with the Super User account only. Also, it is not advisable to change your portal host name frequently or without notifying all employees and customers who are users of your portal. Make sure to send out an announcement with the new URL you are planning to use.
The button for updating the account host name is located in the Company Profile page as well as the Account Management page. The setting is very simple. Just select a new host name and then click "save". When you log off, you will be redirected to the new URL.