Hiding the window location for a window.open call

When I open a window with window.open I always see the path to the window at the top, as shown in the image below ("www.cottonwoodonline.com/sw1.html").  This window is loaded with sw1.html with the code below:

      sw1Ref = window.open('sw1.html', ' ', 'width=' + popup.sw1.width + ', height=' + popup.sw1.height + ', left= ' + (myWidth/2 - popup.sw1.width/2) + ', top=' + popup.sw1.top);

Select allOpen in new window

This is fine for the this menu application but what if I'm opening a window to a secret directory with images and  I don't want to reveal to everyone where this directory is?   How can control what appears in the window address bar?

Thanks
open.png