Object screenoff in "onmouseover"

Object screenoff in "onmouseover"

I really don't know anything about Javascript, but my website has these
lines below, that shows a window in onmouseover. I wonder how to make the
window appear on top of the word when the window is screenoff.
Thanks.
function showLayer(obj){
var div = document.getElementById(obj).style;
div.display = "block";
}