Wiki plugin template

Okay I've launched the wiki.

But why does my CSS conflict on these pages? See the diagonal shaped box on the wiki pages:
http://www.ppcplans.com/wiki/
http://www.ppcplans.com/wiki/main/

CSS Code is:
media="screen"
.drop-shadow {
position: relative;
width: 90%;
}

It works fine on all my other pages. So why not here?