Many Ancestry links are bad because Ancestry changed all of its URL formats a few years back.
The Ancestry external link templates enable repair of the bad links. For example, if you have a old-format URL for an Ancestry Family Tree that looks like this:
http://trees.ancestry.com/pt/AMTCitationRedir.aspx?tid=475790&pid=197186
You can replace that entire URL with the Ancestry Tree template, like this:
{{Ancestry Tree|475790|197186}}
(In that template, the first number is the tid number and the second number is the pid number.) That will generate a URL fpr the person that should work if the content still exists on Ancestry. If you are a subscriber and the resulting URL does not work, try deleting the second number from the template:
{{Ancestry Tree|475790}}
That generates a link to a personal tree, in which you can search for the name of the specific person.
I find this feature very helpful for figuring out what the profile creator had in mind -- so I can propose an appropriate merge, add good sources, correct errors, or otherwise improve the WikiTree profile.