Weird ads showing up in web pages

[Jennifer McLeod]

Hello, Web4Libbers.  

Something odd has been going on here in our library.  For the past
couple of weeks, several of our public-access PCs, as well as the PC at
the reference desk, all of which use Netscape 3.0 to access the web,
have begun to have strange things appear when they access our library's
home page.

What happens varies - icons of ads from Yahoo appear ("win a trip to
France!"), Yahoo's banner itself appears as well, and sometimes our
navigational buttons are rearranged or even repeated.  The ads and
banners REPLACE the pictures we normally have on-screen.   However, when
one clicks on one of these out-of-place images, we are taken to the
appropriate page on our system.  (for example, the "hours" button was
replaced by the Yahoo banner, yet when clicked on our library hours page
was displayed.  It looks normal.)  We even had the picture of our
library building appear twice on the page!  The strange layouts do not
affect the links (apparently).

After a bit of surfing, the page will load normally, but sometimes
hitting reload doesn't reset the page.  

When the source code is revealed, the page looks perfectly okay.  I see
no signs of weirdness on our server.

This does not happen all the time, nor does it happen at a certain time
every day.  Also, it hasn't happened (that I know of) on any of the
staff-only machines (of course, people don't tell me EVERYthing.  :) ). 
It also seems to be ONLY our library's home page, not other pages.  That
is the default "home" page on each machine.

Help!  What could be doing this?  Major mystery!  Could the infamous
cookies be causing images to display on pages at certain times?  (that
is one hypothesis).  Any thoughts, comments, suggestions, mad ravings?
All would be appreciated!


Thank you!

Jen McLeod
CWIS Coordinator
University of Maine