This article talks about the Style element when it's located in the body element.
It is accepted by browser but this is not the standard. The HMTL DTD does not allow it.
But all browsers support it. Mainly because there is no other way to add styling to a fragment of HTML added via an Ajax request.
style in body has the consequences to re-paint the page and may then causes a flash of unstyled content (FOUC).