Help:Cite errors/Cite error references no key

Overview
A footnote used multiple times may be defined with a name:
 * content

To invoke a named footnote:

References may also be defined within the reference list:

List-defined references may be invoked by the standard markup or by use of r.

An explanatory note may include a reference by using #tag:ref:

Where content may include  tags

Issues and resolution
A list-defined reference has an invalid name. Ensure the footnote name is formatted properly.

More than one use of or #tag:ref within list defined references. You can only use or #tag:ref once as a list-defined reference.

Examples
In the example below, a reference with the name excepteur is not named in the References list, since that reference is malformed. This causes a secondary error because the undefined reference is invoked in the References list:

{{pre| Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. {{highlight| }} Curabitur pretium tincidunt lacus.

Bugs

 * Nested refs fail inside references block