You hear it all the time in commercials: "Visit us at www dot company name dot com." And while "www" is commonly used to describe URLs, it's often unnecessary when describing a website address.
If you type "nd.edu" into your browser, it will redirect you to the University's URL: www.nd.edu, but that is the only "nd.edu." website that should use "www."
Notre Dame websites use subdomains—making “www” unnecessary and sometimes incorrect. Depending on the website and the subdomain settings, adding “www” to a subdomain might resolve as expected, but it could also result in a security warning or an error.
Due to these variations in subdomain setups, using "www" to communicate your website’s address should be avoided. When publishing web addresses—especially in print—always test the address before publication to verify that it's working correctly.
As an example, this website would be displayed as:
and never as: