Is there any way in JavaScript to focus the document (content area)?

In HTML 4.01, focus is only discussed in the context of elements such as form controls and links. In HTML 5, it is discussed much more widely. However, how focus works for documents is mostly browser dependent.

You might try:

// Give the document focus
window.focus();

// Remove focus from any focused element
if (document.activeElement) {
    document.activeElement.blur();
}

It is very well supported as well.