edit cross-doc link; add comment

Author: gregsdennis

specs/jsonschema-validation.md

@@ -209,7 +209,8 @@ Omitting this keyword has the same behavior as a value of 0.
 
 The value of this keyword MUST be a string. This string SHOULD be a valid
 regular expression as indicated in
-[JSON Schema Core, section 6.3](./jsonschema-core.md#regex).
+[JSON Schema Core, section 6.3](./jsonschema-core.html#regex).
+<!-- This link assume a publish path, which we don't know yet. -->
 
 A string instance is considered valid if the regular expression matches the
 instance successfully. Recall: regular expressions are not implicitly anchored.