fixed location for... tooltip, pop up frame, iframe?

So, my website has text running down one margin that narratively list the types of maps I make.  I would like each item in this list to be a hyperlink, which when clicked-on (or hovered-over) displays an image and some caption text in the "center stage" space of the page.  I've been using the tooltip widget, which is great in all ways, except that I can't get the target to appear in a fixed location (I can fiddle with the offset, but still, if you hover over one end of the word the target location shifts in that direction).  Any ideas on how to hack the JS code to get this effect, or use a different technique? 

Thanks,

James