Using Tab, it is possible to change focus between controls. However, in several cases - the most notable for me being Windows compiled help files - they only change focus between controls inside a single container; either one with tabs (search/contents/favourites) or content panel, where the help itself is shown.
What I would like to know is whether it is possible to tabulate/change focus between containers/panels? As it stands, I find myself at loss as to how to explore content of the help document without using the mouse.