CSS in IE?

[5th-Level]

My CSS doesn't show up in Internet Explorer. Anyone ever had this problem?

My CSS:

ADDITIONAL CSS DEFINITIONS:

.nav_back {
background-image:url(images/perfect/misc/nav_back.gif);
background-repeat:repeat-x;
width: 877px;
height: 43px;
margin: 0px auto;
}

In Templater:

<div class="nav_back">
CONTENT
</div>