PHP Layout (div) in Firefox 3.6 falsch dargestellt

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de" lang="de">
<head>
    <title>...</title>
    <meta http-equiv="content-type" content="text/html; charset=us-ascii" />
    <meta name="description" content="" />
    <meta name="author" content="" />
    <meta name="keywords" content="" />
    <meta name="generator" content="Webocton - Scriptly (www.scriptly.de)" />
    <link href="style.css" type="text/css" rel="stylesheet" />
    <link href="favicon.ico" type="image/x-icon" rel="shortcut icon" />
<style type="text/css">
/*<![CDATA[*/
    body
    {
        background:url(Bilder/Hintergrund.jpg) #FFF1BE no-repeat top left fixed;
    }
/*]]>*/
</style>
</head>

<body>
    <!-- Header -->
    <div>
        <!-- Logo-Link zur Homepage -->
        <a href="index.php"><img border="0" id="logo" src="Bilder/Logo.png" alt="..." title="..." width="357" height="135" name="logo" /></a>
        <!-- Einfügung der Navigation -->
        <?php
        include 'navigation.php';
        ?>
    </div>
    <!-- Content -->
    <div id="content">
    gfsdfg<br />
    a<br />
    b<br />
    c<br />
    d<br />
    e<br />
    f<br />
    g<br />
    </div>
</body>
</html>

html, body {
}

#logo
{
    float: left;
}

.home
{
    margin-top: 56px; margin-left: 10px; float: left; background-image: url(Bilder/navigation/home_inaktiv.png);
}

.home:hover
{
    background-image: url(Bilder/navigation/home_aktiv.png);
}

.home_aktiv
{
        margin-top: 56px; margin-left: 10px; float: left; background-image: url(Bilder/navigation/home_aktiv.png);
}

.artikel
{
    margin-top: 56px; margin-left: 10px; float: left; background-image: url(Bilder/navigation/artikel_inaktiv.png);
}

.artikel:hover
{
    background-image: url(Bilder/navigation/artikel_aktiv.png);
}

.artikel_aktiv
{
    margin-top: 56px; margin-left: 10px; float: left; background-image: url(Bilder/navigation/artikel_aktiv.png);
}

#content
{
    width: 1016px; height: auto; background-image: url(Bilder/content_bg.png); margin-left: 5px;
}