Have you heard of microformats ?

Microformats are usings predefined XHTML snippets to show common elements in web pages. For example to display a contact, you could use the hCard which allow you to represent a vCard (like those used in most email tools).

Why do that ? The hope is that in the near future, you will be able for example to drag and drop a contact on a web page directly into your contact manager application.

I think I will try to follow those recommendation, so that when the day has come, I will be microformats ready!

UPDATE: the day has already come, (technorati)[http://technorati.com/contacts/] has a small web application that converts and hCard to a vCard and allows your browser to download it and add it to your contact manager.