I am just wondering about phone numbers on HTML web sites when visited by an Ipad or Iphone.

A small box appears saying "call".
Allowing the user to simply hit call rather than entering the number.

Is this functionality done with special HTML tags or is there some format you have to use?

BTW I am not sure if the Iphon/Ipad has this functionality built in or maybe the pages I have seen with this are mobile phone pages only.

Can i do it with a normal webpage?