The Skype plugin for Internet Explorer finds text it thinks is phone numbers and adds controls around it to let the user call the number via Skype. Nasty work. Especially since it also picks up ABNs, company numbers, etc, and tends to break the page layout as well.
To fix it, this meta declaration needs to be added to the head element:
<meta name="SKYPE_TOOLBAR" content="SKYPE_TOOLBAR_PARSER_COMPATIBLE" />