OK, mucked around with it a bit and sorta know what it's supposed to do.
Can't see much use for it though?
This feature puts a movable cursor on your web page and allows you to go up and down like you do in a word document. This makes it really handy as you can select paragraphs and areas easily and quickly.You can enable this by pressing F7 on any page. This might be little slower than your tabbed browsing and the spatial browsing (ability to navigate between focusable elements) but its more precise.