The URL

attribute
contains either a web link or an email address.
The URL attribute value can start with any of the following
text:
- http:// (for example, http://www.examplecompany.com)
- mailto: (for example, mailto:info@examplecompany.com)
- .ftp://
- news://
- https://
- \\Server\folder\file.txt (for example, Microsoft® Windows®)