You can do that using our Stylehelper skin object.

http://www.40fingers.net/WeblogsNews/... 

You need to donload and install it and add this to your skin:
<%@ Register TagPrefix="fortyfingers" TagName="STYLEHELPER" Src="~/DesktopModules/40Fingers/SkinObjects/StyleHelper/StyleHelper.ascx" %>

To register the control in the skin and add

<fortyfingers:STYLEHELPER ID="SH1" AddHtmlAttribute="xmlns:fb,http://www.facebook.com/2008/fbml|xmlns:og,http://opengraphprotocol.org/schema/" 
runat="server" />

To add the two attributes.
The first one would already be added correctly if you use an XHTML doctype for your skin.
(which you can do with a skinname.doctype.xml file or with our skin object)

Add:

doctype="XHTML 1.0 Transitional"