Simple CSS problem - I think

programming web dev
1

I’m a total newbie w/ Dreamweaver and I can’t get a Flash element to center. It was centered originally and I changed something, now it won’t I have a class called .centered that only includes auto left and right margins, but these are crossed out in my Flash element with the comment “Does not apply to your selection because it is not inherited. It is applied to an enclosing tag.” I can’t figure out how to fix this.

HTML:
 
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>SUNY Plattsburgh PHPAC</title>
<script src="Scripts/swfobject_modified.js" type="text/javascript"></script>
<link href="PHPACStyles.css" rel="stylesheet" type="text/css">
</head>
<body>
<div id="wrapper">
  <header >
    <h1>Plattsburgh State Pre-Health Professions Advisory Committee</h1>  
  </header>
<div class="centered" >
    <object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" width="860" height="700" id="FlashID" title="DropDown">  etc. . . .
 
 
 
CSS (PHPACStyles.css):
 
@charset "utf-8";
body {
                }
#wrapper {
                width: 100%;
                clear: left;
                background-image: url(WhiteCaduceusBG.gif);
                }
#top {
    overflow: hidden;
}
 
h1 {
                font-size: 52px;
                margin-top: 9px;
                margin-bottom: 24px;
                text-align: center;
                text-shadow: 10px 4px 10px #333333;
                font-family: Constantia, "Lucida Bright", "DejaVu Serif", Georgia, serif;
                background-color: #CC0000;
                color: #FFFFFF;
                margin-left: auto;
                margin-right: auto;
                border-radius: 3px;
                border-spacing: 4px 4px;
                -webkit-box-shadow: 5px 5px 10px #999999;
                box-shadow: 5px 5px 10px #999999;
                border: thick ridge #CCCCCC;
                padding-left: 10%;
                padding-right: 10%;
}
 
.centered {
                margin-left: auto;
                margin-right: auto;
}