Im trying to create a website (obviously) but when I try to position one div next to another the background in one stops working

I dont know why this isnt working or how to fix it. By the way I'm very new to html and css so my code is probably sloppy. Thank you in advance for any help you can give.
HTML
Code:
<!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">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Productivity</title>
<link href="mainstyles.css" rel="stylesheet" type="text/css" />
<link href='http://fonts.googleapis.com/css?family=Ubuntu+Condensed' rel='stylesheet' type='text/css'>
</head>
<body class="background webfonts" >
<div id="header" class="headerdiv" >
<span class="header"> My </span>
<span class="headeremph"> Productivity </span>
<span class="header"> Website </span>
</div>
<div id="conent_container" class="contentdiv">
<img src="assets/content_header.png" />
<div id="content_main-container_bg" class="maincontentbg" >
<div id="content_text" class="contenttextdiv">
<div id="title_container" class="contentpagetitle"> Page Title goes here </div>
<span class="contenttitletext">Content Title Goes Here</span><br />
<span class="contenttext"> Content...content goes here (need bottom margin of ~5px)</span>
</div>
</div>
<div id="vert-nav-header_container" class="vert-nav-header"><img src="assets/vert_nav_header.png" /></div>
</div>
</body>
</html>
CSS
Code:
@charset "utf-8";
/* CSS Document */
.webfonts {
font-family: 'Ubuntu Condensed', sans-serif;
}
.background {
background-image:url(Pictures/background_texture.jpg);
background-attachment:fixed;
background-position:center;
}
.headerdiv {
margin-top:30px;
margin-left:30%;
}
.header {
font-size:36px;
color:#CCCCCC;
}
.headeremph {
font-size:43px;
color:#999999;
}
.contentdiv {
margin-left:auto;
margin-right:auto;
margin-top:30px;
width:631px;
}
.maincontentbg {
background-image:url(assets/main_content_repeat.png);
background-repeat:repeat-y;
background-position:center;
}
.contenttitletext {
color:#CCCCCC;
font-size:24px;
}
.contenttext {
color:#CCCCCC;
font-size:16px;
margin-left:15px;
margin-bottom:15px;
}
.contenttextdiv {
margin-left:5px;
}
.contentpagetitle {
font-size:36px;
color:#999999;
margin-bottom:5px;
}
.vert-nav-header {
margin-left:50px;
}