Alright so, here is this page:
http://thepilotsworld.com/article.php?newsid=2

As you can see there, the white background height isn't adjusting to the content placed within.
I've tried several things to fix this.
So here's the style:

HTML Code:
@charset "utf-8";
/* CSS Document */

body
{
	background:url(images/1600x1200.jpg)
}
#wrapper
{
	width: 950px;
	height: auto;
	margin: 0 auto;
	-moz-box-shadow: 0 0 5px 5px #888;
	-webkit-box-shadow: 0 0 5px 5px#888;
	box-shadow: 0 0 5px 5px #888;
}
#header
{
	width: 950px;
	height: 200px;
	background:url(images/banner.png);
	margin: 0 auto;
}
#mainContent
{
	width: 950px;
	min-height: 600px;
	height:auto;
	background-color:#FFF;
	margin-top: -20px;

}
.message {
font-family: "Trebuchet MS", Tahoma, Helvetica;
font-size: 12px;
}
hr {
	width:920px;
	background: #fff;
	border: 0;
	margin: 0px;
	border-bottom: 1px solid #e3e1d9;
}
.header {
font-size: 12px;
padding: 15px;
width: 900px;
float: left;
margin-top: 15px;
margin-bottom: 15px;
text-align: left;
}
.title {
font-family: "Trebuchet MS", Tahoma, Helvetica;
color: #423F44;
font-size: 25px;
padding-bottom: 6px;
}
a img { border:0 }
a:hover { color: #999; }
a { color: #666; }
.CommentHeader {
padding: 15px;
width: 890px;
float: left;
text-align: left;
background-color:#D3D3D3;
margin-left:15px;
opacity:0.5;
min-height:51px;
}
.CommentAuthor {
font-family: "Trebuchet MS", Tahoma, Helvetica;
color: #333;
font-size: 15px;
text-shadow:0 1px 0 #666;
}
.CommentMessage {
font-family: "Trebuchet MS", Tahoma, Helvetica;
color: #333;
font-size: 15px;
}
.button {
	border: 1px solid #ccc;
	background: #ddd;
	font-family: "Trebuchet MS", Tahoma, Helvetica;
	color: #222;
	font-size: 12px;
	text-decoration:none;
}
And here is the page:
PHP Code:
<?php session_start(); 
 
?>
 <!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="style.css" />
<link type="text/css" href="menu.css" rel="stylesheet" />
<link href='http://fonts.googleapis.com/css?family=Open+Sans' rel='stylesheet' type='text/css' />
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="menu.js"></script>
<meta charset="utf-8">
<title>The Pilot's World</title>

</head>
<body>
<?php include("head.php"); ?>
<div id="mainContent">
<center>
<?php
$host
="*******"// Host name 
$username="*********"// Mysql username 
$password="**********"// Mysql password 
$db_name="************"// Database name 
$tbl_name="news"// Table name
mysql_connect("$host""$username""$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");   
$activenews $_GET['newsid'];
$activenews stripslashes($activenews);
$activenews mysql_real_escape_string($activenews);
$result mysql_query("SELECT * FROM $tbl_name WHERE id='$activenews'");
$count mysql_num_rows($result);
while(
$row mysql_fetch_array($result)){
$count mysql_num_rows($result);
      echo 
"<div class='header'>";
    
        echo 
"<div class='title'>".$row['title']."</div>
        Published on <a href='#'>"
.date('jS \o\f F, Y'$row['date'])."</a> by <a href='user.php?user="$row['author']."'>"$row['author']."</a><br><br><hr><br>";
        echo 
"<div class='message'>".$row['message']."</div><br><br><hr><br>";
      echo 
"</div>";
      if (
$count == 0){
         echo 
"<center><p>News not found!</p><p>&nbsp;</p></center>";
      }
}
$result mysql_query("SELECT * FROM newscomments WHERE newsid = '$activenews' ORDER BY date DESC");
$even 1;
while(
$row mysql_fetch_array($result))
{
    if(
$even == 1)
    {
        echo 
"<div class='CommentHeader'>";
        echo 
"<div class='CommentAuthor'>".$row['author'].":</div><br />";
        echo 
"<div class='CommentMessage'>".$row['message']."</div></div>";
        
$even 0;
    }
    else 
    {
    if(
$even == 0)
    {
        echo 
"<div class='CommentHeader' style='background-color:#F5F5F5'>";
        echo 
"<div class='CommentAuthor'>".$row['author'].":</div><br />";
        echo 
"<div class='CommentMessage'>".$row['message']."</div></div>";
        
$even 1;
    }
    }
    
}
if(isset(
$_POST['comment']))
{
    
$comment stripslashes($_POST['comment']);
    
$comment mysql_real_escape_string($comment);
    
$timestamp time();
    
mysql_query("INSERT INTO newscomments (newsid,author,message,date) VALUES ('$activenews','".$_SESSION['myusername']."','$comment','$timestamp')");

}
if(isset(
$_SESSION['myusername']))
{
    if(
$even == 1)
    {
        echo 
"<div class='CommentHeader'>Post a comment:";
        echo 
"<form action='article.php?newsid=$activenews' method='post'>
              <input type='text' name='comment'>
              <input type='submit' value='Post' class='button'>"
;
        echo 
"</form></div>";
        
$even 0;
    }
    else 
    {
    if(
$even == 0)
    {
        echo 
"<div class='CommentHeader' style='background-color:#F5F5F5'>Post a comment:";
        echo 
"<form action='article.php?newsid=$activenews' method='post'>
              <input type='text' name='comment'>
              <input type='submit' value='Post' class='button'>"
;
        echo 
"</form></div>";
        
$even 1;
    }
    }
}
echo 
"<br>";
?>
</center>
</div>
<div id="footer">
</div>
</body>
</html>
So does anyone have a clue WHY this is happening.
I also have another page, where the height DOES adjust. And I already tried replacing the HTML stuff from that page into this one but no luck.

Yours sincerely,
Kevin Houghton

PS. I'm new here, I'm sorry if I've placed this in the wrong section.