in the ?

Hello

While trying to clean up my configuration a bit, I came across this tag, injected (?) twice into the head-part of my wordpress-blog.

Does anybody have an idea where it comes from, and / or how to get rid of it?
(Or, to put it more generally, how do I find out which plugin does what to my configuration/templates? – except through try and error – I have been testing quite some plugins and am not sure if they really did not alter my files. I only know I didn’t … )

Thanks very much for directions / Tips / …

david