Forumlar / Cotonti / Support / MarkItUP skining help

Im trying to make a custom look for the markitup.
The problem is the Background of the preview frame.
I'w tried to put in the css this:

.markitup (body\PreviewFrame body) {
overflow:hidden;
background:red;
border:1px solid #3C769D;
width:99.9%;
height:130px;
margin:0px 0;
background-image:none;
}

but it doesnt react.Still takes the background picture from the general css's 'body'

It begins to read the background color only after i erase the:
"$style = '<link rel="stylesheet" type="text/css" href="skins/'.$skin.'/'.$skin.'.css" />'."\n";"
from the markitup.ajax.php

Please help