CSS menu explanation wanted

[Nancy Wallace]

Hello!

I figured out the solution to my problem, however I am utterly
clueless as to why it works. Could someone explain it to me?

Here was my problem:

I have a CSS menu with a image change underneath the menu upon
different menu item hovers. The menu items themselves are also
images, with partial transparency so the changing image underneath can
be seen. I easily got this to work with every browser except IE
(shocking, really). In IE, I had one of two undesireable situations:
1) The hovered menu items had the necessary transparency, however the
image underneath didn't change; or 2) the image underneath changed
correctly with the hovering, however the hovered menu item lost its
transparency.

The simple addition of:

filter:alpha(opacity=100);

in the hovered menu item's style fixed my problem, and now everything
works as it should. WHY?!?

If you want to see the code:

www.computer-lizards.com/oc/index.htm
www.computer-lizards.com/oc/style.css
www.computer-lizards.com/oc/menu.css
www.computer-lizards.com/oc/ie6hack.css
[I know the code is ugly right now, it's under development...]

Thanks!
--Nancy
(e-mail address removed)