CSS - Center Block Keeps Dropping On Rescale

http://www.outincenterfield.com/mt/

/*
THEME NAME: Diurnal
THEME URI: http://ntuat.wordpress.com/
DESCRIPTION: This flexible 5-in-1 theme changes according to the time of day
VERSION: 1.0
AUTHOR: Carolyn Smith
AUTHOR URI: http://not-that-ugly.co.uk/
TEMPLATE: sandbox
*/

/* use any structure in /sandbox-layouts; more details in the readme*/
/* included here for Movable Type */


/* links to time-specific stylesheets */
@import url('sunrise/style.css');
@import url('morning/style.css');
@import url('afternoon/style.css');
@import url('sunset/style.css'); 
@import url('night/style.css'); 

div#container {
    margin-left: auto;
    margin-right: auto;
    width: 1000px;
}
div#content {
    margin: 0 400px 0 0;
}
div.sidebar {
    float: left;
    overflow: hidden;
    width: 180px;
}
div#primary {
    margin: 0 0 0 -400px;
}
div#secondary {
    margin: 0 0 0 -200px;
}
div#footer {
    clear: left;
    width: 1000px
}


body {font: 0.75em arial, helvetica, verdana, sans-serif;
margin:0;
padding:0;
color:#444}

#container {background:#fff;}

#content {
padding:0 10px 0 10px}

/* header */
#header {height:200px;}

#header h1 {font:3em 'century gothic', futura, serif;
margin:0;
padding: 0 10px 0 10px;}

#blog-description {padding:7px 10px 0px 10px;
color:#fff}

.skip-link {display:none}



/* prev/next links */
.navigation {margin:1em;
text-align:center;
width:95%;
height:1em}

.nav-previous {float:left;
text-align:left;
width:45%}

.nav-next {float:right;
text-align:right;
width:45%}

.nav-previous a {padding-left:20px;
background:url(leftarrow.gif) center left no-repeat;}

.nav-next a {padding-right:20px;
background:url(rightarrow.gif) center right no-repeat;}

span.meta-nav {display:none}


/* page navigation */
#menu ul li {
margin:0;
padding:0;
display:inline;
font:1.2em 'century gothic', futura, sans-serif;
}

#menu ul li ul {margin:0;
display:inline;
font-size:0.8em;
}

#menu ul li a {
padding: 3px 20px 3px 10px;
letter-spacing:0.05em;
}





/* sidebar stuff */
.sidebar {margin:0;
padding: 10px;
background:#fff}

.sidebar h3, .comments h3, #respond h3 {letter-spacing:0.05em;
margin:0;
padding:7px 10px 3px 20px;
font: 1.4em 'century gothic', futura, sans-serif}

#menu ul, .sidebar ul {list-style:none;
margin:0;
padding:0;}

.widget, .sidebar li.linkcat {border:1px #ccc solid;
margin-bottom:2em;}

.sidebar ul li, #wp-calendar caption {background:#f0f0f0 url(greybk.png) top left repeat-x;
border:1px #ccc solid;}

.sidebar h3 {border:1px #ccc solid;}

.sidebar ul li ul li, .sidebar ul li div {background:#fbfbfb;
border:0;
padding:3px 10px 3px 10px;}

.sidebar ul li ul li ul li {
padding-left:20px;
background:url(rightarrow.gif) center left no-repeat;}



/* posts & comments */
.post, body.page div.hentry, .comment, .trackback, .pingback {border:1px #ccc solid;
margin:10px 0 10px 0}

.entry-title, .comment-author {letter-spacing:0.05em;
margin: 0;
background:#f0f0f0 url(greybk.png) top left repeat-x;
padding:5px 10px 0px 10px;
font: 2em 'century gothic', futura, sans-serif}

abbr.published {border:0;}

.entry-date, .comment-meta, #trackbacks-list div.comment-author  {
text-transform:uppercase;
font-size:0.9em;
margin:0;
background:#f0f0f0; 
padding:0px 10px 5px 10px;}

.entry-date {background:#f0f0f0 url(clock.gif) top left no-repeat;
padding-left:20px}


#trackbacks-list div.comment-author {font-family: arial, helvetica, verdana, sans-serif;
border-bottom:1px #ccc solid;
letter-spacing:0em;
padding-top:5px}

.comment-meta {border-bottom:1px #ccc solid;}

.comment p, #trackbacks-list p {padding:0px 10px 0px 10px;
background:#fbfbfb;}

.entry-content {line-height:1.4em;
padding:10px;
background:#fbfbfb;
border-top:1px #ccc solid;
}

.entry-meta{
clear:both;
background:#f0f0f0;
border-top:1px #ccc solid;
padding:5px 10px 5px 10px}

.meta-sep {padding-left:18px;
color:#f0f0f0;}

li.bypostauthor div.comment-author {background:#f0f0f0 url(starbk.png) top left repeat-x}



/* forms */
input, textarea {background:#f0f0f0 url(greybk.png) top left repeat-x;
border:1px #ccc solid;
color:#444;
font:1em arial, helvetica, verdana, sans-serif;
overflow:auto}


#commentform #submit {margin:10px 0 10px 0;
color:#333}

#searchform div{background:#f0f0f0;
margin:10px}

#searchform submit {color:#333}


/* calendar */
#calendar h3 {display:none}

div#calendar_wrap {padding:0;
background:#f0f0f0 url(greybk.png) top left repeat-x;}

#wp-calendar {width:100%;
background:#fbfbfb;}

#wp-calendar caption {font:1.4em 'century gothic', futura, sans-serif;
margin:0;
padding: 5px 0px 5px 20px;
text-align:left
}

#wp-calendar td {text-align:center;
border:#ccc 1px solid;
background:#f0f0f0 url(greybk.png) repeat-x;}


#wp-calendar tfoot td {
background:#fbfbfb;
border:0;
}

#wp-calendar td.pad {border:0;
background:#fbfbfb}

td#today {
background:#ccc;
border:#999 1px solid}




/* image handling */
#content img {max-width:98%;}

#content, .sidebar {overflow:hidden}

a img {border:0}

.alignright {
float:right;
margin:5px}

.alignleft {
float:left;
margin:5px}

.center {
margin:auto;
display:block;
}


/* getting asides to LOOK like asides */
body.home div.category-asides {
margin:20px 0px 20px 0px;
padding:5px 10px 5px 10px}

body.home div.category-asides *{
display:inline;
}

body.home div.category-asides .entry-content {border:0;
font-size:1em;
line-height:1.5em;
padding:0}

body.home div.category-asides div.entry-meta {background:#fbfbfb;
margin:0;
border:0
}

body.home div.category-asides .entry-title, 
body.home div.category-asides .entry-date,
body.home div.category-asides .author, 
body.home div.category-asides .meta-sep,
body.home div.category-asides .cat-links    
{display:none}


/* html elements */

a {text-decoration:none}

blockquote {border:1px #ccc solid;
padding:5px}

h2 {font: 2em 'century gothic', futura, sans-serif;
margin:10px 0 -10px 0;
}

.hentry ul {list-style-image:url(rightarrow.gif)}

#footer {
background:#f0f0f0 url(greybk.png) repeat-x;
text-align:center;
border-top:#ccc 1px solid;
padding:10px 0 10px 0;
}
 

#nav ul {
margin: 0 0;
padding: 0 0;
list-style-type: none;
}

#nav ul li {
float: left;
position: relative;
width: 10em;
}

#nav ul li ul {
display: none;
position: absolute;
top: 1em;
left: 0;
}

#nav ul li > ul {
top: auto;
left: auto;
clear: left; 
}

#nav ul li:hover ul, #nav ul li.over ul {
display: block;
}

<div id="nav"><ul id="rootul">
<li><a href="#">Link One</a>
<ul>
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link 2</a></li>
</ul>
</li>
<li><a href="#">Link Two </a>
<ul>
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link 2</a></li>
</ul>
</li>
<li><a href="#">Link Three </a>
<ul>
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link 2</a></li>
</ul>
</li>
<li><a href="#">Link Four </a>
<ul>
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link 2</a></li>
</ul>
</li>
<li><a href="#">Link Five </a>
<ul>
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link 2</a></li>
</ul>
</li>
</ul>
</div>

<script language="javascript" type="text/javascript">
startList = function() {
if (document.all&&document.getElementById) {
navRoot = document.getElementById("rootul");
for (i=0; i<navRoot.childNodes.length; i++) {
node = navRoot.childNodes[i];
if (node.nodeName=="LI") {
node.onmouseover=function() {
this.className+=" over";
  }
  node.onmouseout=function() {
  this.className=this.className.replace(" over", "");
   }
   }
  }
 }
}
window.onload=startList;
</script>