In one of our SharePoint 2010 sites we have a note field with Rich Text enabled and Rich Text Mode set to Full Html.
We found out today that SharePoint 2010 automatically converts links (a tags) in the above case by “helpfully” removing the site name
i.e.
<a href=’http://server/site/library/document.docx’>link</a>
becomes
<a href=’/site/library/document.docx’>link</a>
in our case we were using this in the body of an email to 3rd parties and the removal of the server gave us grief.