Hello @nancyr887 ,
This is the source description used for contacts whose source is a legacy landing page. The legacy landing pages, just like the newer landing page forms, are shareable via a URL - meaning they can be hosted anywhere you want essentially. If your organization used them in the past, it may be a link on your website, in social posts, or as the default for your emails' webpage versions. Typically nowadays, unless you're using the legacy LPs to have multiple list selections for signups, the only common source is the webpage version of emails, which are what's provided when a contact clicks the forward-to-friend button you made add to an email, or when you share your email on your social pages.
If you need to update your legacy landing page, you can do so by going to Sign up forms > basic landing pages > Sign up form. Unless your organization has made multiple in previous years, the only two that should appear are the "sign up form" and the "update profile form."
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