I never heard about Lavabit before, I'm going to try it out. But I have no clue what web interface they have, maybe the parent can tell?
When you view an email, only text is shown. You can "View as HTML", but images are blocked. http://i.eho.st/pp2fukzy.png
Personally, this renders the web interface useless to me, so I view my email through Outlook.
Makes sense, it's sort of the goto open source webmail app.