With JavaScript you can mess with mouse coordinates. The top left corner of your screen is Y=0 X=0 as you move further to the right X increases as you move further down the page Y increases.
As for the TAB thing...It's determined by the tabindex attribute I believe if you put a -1 as the argument it means the tab will not stop on that object. It starts at 0 and continues all the way for as long as you have numbers.
Code:
[img]/someImage.jpg[/img]