I added this:
This is built into HTML5 according to the spec:
If target is the top of the document, then scroll to the beginning of the document for the Document
In other words, it's a special case and you don't need to specify an ID for the top of the page.
See also MDN:
Note: You can use the special fragment "top" to create a link back to the top of the page; for example
<a href="#top">Return to top</a>