Line 12, Column 0

Hello
 
On the page 

 <http://validator.w3.org/check?uri=http%3A%2F%2Fbernhard.lauber.to%2F>
http://validator.w3.org/check?uri=http%3A%2F%2Fbernhard.lauber.to%2F

I get the error 

 Error <http://validator.w3.org/images/info_icons/error.png> Line 12,
Column 0: 14 +0200 <a href='data/books.

which doesn't mean anything to me.
 
Please help.
 
Thanks
Bernhard Lauber