Hi,
When I look at the skype page about adding it to your web page it shows that javascript must be added for a call me button.
The markup you posted does not look malicious and seems like it could be added to the page by the skype javascript. Maybe you have forgotten that you added javascript somewhere (like in your master page) and not just a link. Or maybe Skype is integrated with your web browser (like a browser plugin) and is able to update the page markup even without javascript. I would be more concerned about javascript in the page than I would about extra html markup. If there is any skype javascript in the page that you did not add yourself it certainly is not coming from mojoPortal as we don't have anything skype related built in.
I would view the source of your page carefully for any skype javascript and try viewing your page form different web browsers or from different machines that don't have skype installed.
Hope that helps,
Joe