adjacent hyphens within comment

Cause:

This is due to too many hyphens "-" in the declaration of a comment. A comment is defined like this <!-- comment -->. Also, comments may not contain two hyphens next to each other.

Example:

Good<!--- comment --->
Good<!-- comment -->

Example:

Good<!-- comment -- other comment data -->
Good<!-- comment - other comment data -->

Solution:

Remove the additional hyphens.

References: