Edward,
I'm going to make a guess that you are using FrontPage Hover Buttons in your
site. If that's the case, the problem you're seeing is caused by the fact
that the Hover Buttons require a visitor to have a Java Virtual Machine
(JVM) installed on their computer in order for them to work. Due to legal
disputes with Sun, Microsoft discontinued sending out a JVM with Windows XP.
That means if you, or one of your visitors has Windows XP and hasn't
manually installed a JVM (such as the one from Sun:
www.java.com) then the
buttons won't work.
Because you, as the web developer, have no control over your visitor's
computer configuration, and because the Hover Buttons fail so terribly
(meaning the links don't work without a JVM) the general recommendation is
to not use them at all. If you prefer to have a hover effect on your links,
take a look at a JavaScript solution. JavaScript has nothing to do with
Java except for the name similiarity. With most good JavaScript hovers,
even if your visitor has JavaScript turned off, the links will still work.
They just won't look as cool.
Here's one online code generator that can help get you started:
http://javascript.internet.com/generators/preload-images.html
I hope that helps.