This is kind of a Public Service Announcement.
I am sure there are a lot of you, like myself, who are faced with weekly errors/suggestions for links to sources that used to work and are now broken.
There is nothing in our guidelines that indicate that a link is required. It says that the citation much have enough information that another person can find the source. However, most people add a link, as that is the easiest way to get to the source and it saves time of creating a complete source citation. Our guidelines indicate a need to describe the source completely. Such as "US Census, 1900", database online. Home Township, Small Town, Washington, USA; pg. 100, family 10, dwelling 15, lines 150-157; June 1, 1900; National Archives Microfilm M-10, Roll 100" or Anderson, Robert Charles. The Great Migration Begins: Immigrants to New England 1620-1633. Boston, MA: NEHGS, 1995. Volume I, pp 126-130.
The Pre-1700 certification process indicates that you should provide who made the record, what the record is, when the record was made, and where you found the record.
So, you can use a link, or create a "COMPLETE" citation.