You can easily simulate a popup window using DHTML together with div and span tags. Start off by hiding the div area then use javascript to unhide the div tag when required.
rollover here
This is only visible if your mouse rolls over the above text
Obviously you can change the div border and colours, size, location and position to suit.
The text is spiderable but it will probably not be spidered as the div tags begins life being hidden.
Making popups via DHTML