Download page Registering a Salesforce Sites Domain.
Registering a Salesforce Sites Domain
Your company's Salesforce Sites domain is used for all the sites that you create. You must register your company's Salesforce site domain to create public websites and applications that are directly integrated with your Salesforce.com organization—without requiring users to log in with a username and password. Your Salesforce site domain must be unique and must consist of only alphanumeric characters. Salesforce.com recommends using your company's name or a variation of your company's name, such as 'mycompanyportal.'
You cannot modify your Salesforce site domain name after the registration process.
To register your Salesforce Sites domain
Go to Setup > in the Quick Find Box, search and select Sites.
Enter a unique name for your Salesforce Sites domain. A Salesforce Sites domain name can contain only alphanumeric characters and hyphens and must be unique in your organization. It must begin with a letter, not include spaces, not end in a hyphen, and not contain underscores or periods.
You can't modify your Salesforce Sites domain name after you have registered it.
Click Check Availability to confirm that the domain name you entered is unique. If it isn't unique, you are prompted to change it.
Read and accept the Sites Terms of Use by selecting the checkbox.