The content inside an editable region is either editable itself, or
is inside a contenteditable="false" subtree. In the first case,
it should not be focusable since it is editable. In the second
case, it should not be focusable since the entire non-editable
region is treated as a special single entity for the purposes of
selection and caret movement, and having something focusable in
the middle of such a subtree breaks that model.
The content inside an editable region is either editable itself, or
is inside a contenteditable="false" subtree. In the first case,
it should not be focusable since it is editable. In the second
case, it should not be focusable since the entire non-editable
region is treated as a special single entity for the purposes of
selection and caret movement, and having something focusable in
the middle of such a subtree breaks that model.
Ehsan Akhgari
Carsten "Tomcat" Book