Mitch, instead of using your script, add this to the "Extra Properties" section of the Style you want to turn upside-down.

body {
    width: 100%;
    height: 100%;
    -moz-transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    transform: rotate(180deg);

This will allow users to turn OFF the upside-down by selecting a different style.
You could also just duplicate your main style, add this to it and call it "main upside-down" or whatever. Then set that as the default style for the day smile dont forget to reset your default style to the correct one when you're done having fun.

Current developer of UBB.threads PHP Forum Software // 7.7.3 released!
isaac @ // my forum @