You are right, the CSS fixes added by the Maps plugin are added to the body (not valid) rather than the head (valid).
I can't see why it has been done like that and have requested that this be changed.
I spoke with the developers the other day about removing the action which adds this CSS on pages where it is needed and they confirmed that the action is added in such a way that it cannot be removed.
So, currently there is no way to fix this I'm afraid.
I am escalating your thread so the issue can be investigated further, and I'll update you when there is any news.
Thanks a lot. I suppose this code loads in every subpage (although I haven't checked that). Could you provide me with some code snippet (to insert into function.php file) to remove the unnecessary source code from the main page only?
Sorry, I can't. The way the CSS is added it is impossible to remove without disabling the maps plugin entirely.
I raised this issue with the developers the other day who confirmed that is currently the case.
But they should be able to fix adding the CSS to the head rather than the body so that the page validates, but we'll need to wait for them to confirm that.