(Does not answer the question but is a useful link; note in particular that "visual separators" are optional.)
I assume you started out with the same random searches I did, generally leading to the unhelpful suggestion that you might include user-agent detection. Which kinda defeats the purpose of having a phone number in the raw html :(
Does your 404 page act as if you had simply typed in the URL example.com/tel:555-et cetera? If so, you should be able to make a rule to intercept requests beginning in "tel" and send them to a custom page. The rule will only be seen by devices that don't recognize "tel"; it won't interfere with telephone users.
Msg#: 4576962 posted 1:15 am on May 24, 2013 (gmt 0)
...results in a 404 page when clicked from a PC. <snip> "Firefox doesn't know how to open this address, because the protocol (tel) isn't associated with any program."
Now I am confused. Where does the 404 come in?
If the browser steps in before even sending a request to the server, then it isn't your problem. The only way to prevent it is to deploy user-agent detection ahead of time, so the tel: links are only displayed if the user is on the right kind of phone. Or if-- oh, ###, now it gets complicated-- their computer really can make phone calls. (This is a closed book to me, but I have just this moment remembered my father telling me that his computer dials for him. That's a desktop, not mobile-of-any-kind. And no, he's not on a dialup modem connection ;))
You may still be able to treat it as a non-problem if the links are designed so it's very obvious they lead to a phone call, not to another page. Of course there will always be those users who expect their computer to be able to act on all links all the time everywhere...
Msg#: 4576962 posted 2:45 am on May 24, 2013 (gmt 0)