URI fragment syntax

Would whoever told me that HTML fragment identifiers (aka anchors, that which appears after the # in a URI) cannot start with a number please remind me which spec says that?

I certainly remember reading it in response to that person's email, and changed my permalinks to include the word "item" in front of the number. I've also seen browsers NOT work with fragement identifiers that start with a number, so I know this isn't just a non-issue.

Update: Seth found it; it was actually a message on the Conversant support site.

Written on September 20, 2001