JavaScript and pop-up text

[ITS: Sean E. Crumley]

I'm currently designing pages for our younger Library 
customers that have explanatory text message pop up upon 
mousing over a button. I'd appreciate any help or insight on 
the following questions.

1) The pop up text is in the form of a graphic, as is text 
on all web sites I've referred to for inspiration. For reasons 
of economy of bandwidth, I'd prefer to be able to pop up 
actual text. If this can indeed be done, I'd appreciate a 
pointer.

2) In cases where the browser has disabled JavaScript (as 
can Netscape Navigator), doesn't support MouseOver events 
(as I imagine MS Internet Explorer doesn't) or simply 
doesn't support JavaScript at all, can I safely assume that 
graphic files called for in the script are left on the 
server?

3) Is there a way to force reload the submerged images on a
page? Even if I clear my cache, my browser won't release an
older version of the pop-up image and display the newest
version (the server is running on a vax, by the by). To
force the most recent pop-up file to display, I must purge
all previous versions on the server AND clear my browser's
cache. I can live with that, I suppose, but I'd like to know
why my browser sentimentally clings to these older images,
long after its cache has been evacuated. 

Thanks in advance to any respondees.
______________________________________________________________________
Sean Emmett Crumley              <scrumley at queens.lib.ny.us>
Webmaster                         Vox: (718) 990-8652
Queens Borough Public Library     Fax: (718) 523-3860
89-11 Merrick Boulevard           http://www.queens.lib.ny.us
Jamaica, NY 11432
  *Standard disclaimers apply: Opinions expressed are mine alone*