Add a comma before the URL

Error²Federal courts, Illinois courts21st and 22nd editions

A web address is appended at the end of the citation and separated from it by a comma; every web citation printed in either edition shows that comma.¹

1. 1R. 18.2.2 Citations to Web-Based Sources.
2. 2An error: the rule in note 1 allows one form, and this is not it.