Is there some compelling reason for using HTML5?
It's well known that PayPal code doesn't validate in XHTML 1.1 strict documents types probably for the same reasons it doesn't validate in HTML5.
One solution is to modify the code:
Or, if it ain't broke, don't fix it.
The compelling reason that it is HTML5 is that I'm using The Bootstrap Theme as a starting place.
I will see if I can fiddle with the code around the button but I have a feeling that the button itself is calling that in.
Thanks for the link
I had the same problem with a site I was working on. When I validated my code, I got the same string of errors you described.
I fixed the problem by adding a style attribute on the image tag. Also it is a good idea to add to the alt="" tag.
Here's a Pastebin of the code I used. I don't recommend copying it onto your site as it leads to a payment screen for my site. Just look at the <img> tag and notice that the width=1 and height=1 have been removed from the end. As has the border="0".
Hope this helps!