Style attributes

In the WD-style draft, it states that the STYLE attribute is "A text
string providing rendering information specific to this element." I
couldn't find the specification in the CSS draft of exactly which parts
of the grammar are allowed in the STYLE attribute.  Could a sentence be
added to the draft stating that only CSS1 properties are valid in the
STYLE attribute? In the May 5 draft, that would be chapter 5.

While I'm on the subject of "not very clearly specified", the value of
"middle" for "vertical-align" is defined as "align the middle of the
element", but I couldn't find a definition of just what this means.
Should it be the middle of the "x", or "X"? Or the middle of the