Custom Domain (My Domain) Link Added to the Salesforce Login Page

The login page has a link users can click to specify a subdomain for logging in.
Available in: Performance, Unlimited, Enterprise, Developer, Professional, and Group Editions.

If the administrator created a custom domain for the organization using My Domain, users can click the Log in to a custom domain link to provide the existing domain name and log in. A custom domain is in the form where universalcontainers is a name selected by the administrator. The administrator should provide the correct domain name and a specific login page for the organization’s users. If those users are directed to the page, they can use the Log in to a custom domain link to log in.

This link isn’t available for Internet Explorer versions earlier than 10.0.