Using custom URL protocol handler?

Oho, if I have the following links:

<a href="vnd.sun.star.webdav://test.rtf">test.rtf</a>
<a href="vnd.sun.star.webdav:/lino/media/webdav/test/test.doc">test.doc</a>

then FF asks me:


My decision is save in Firefox’s Tools ‣ Options ‣ Applications where I can also later change it again.

When I do the same with a fictive protocol foofoo:

<a href="foofoo://test.rtf">test.rtf</a>
<a href="foofoo:/lino/media/webdav/test/test.doc">test.doc</a>

The I get another reaction: