CSS - Why Won't 'text-align' Work?

Hi,

The text in my navigation bar is slightly off-centre, even though I have applied the text-align:centre property in my style sheet. Is there anything obvious that would be throwing it off?

Any help would be greatly appreciated.

Jimmy

Here is my style sheet:

body
{
padding:0px;
margin:0px;
background-color:#ffffff;
background-image:none
background-repeat:no-repeat;
font-family:verdana, arial, Helvetica, sans-serif;
font-size:11px;
color:#333;
}
/*--------------------DIVs------------------------------*/
div#pagecenter
{
margin: 0 auto;
width: 1024px;
background-color:#ffffff;
}

div#header
{
height:312px;
background-color:#ffffff;
background-repeat:no-repeat;
background: ((address blocked: See forum rules));
padding:5px;
text-align:right;
text-display: none;
color:#FFFFFF;
}

div#desc
{
visibility: hidden;
text-align:left;
}

div#sitename
{
visibility: hidden;
}
div#oup h1 a {
margin-top: -30px;
margin-left: 10px;
margin-right: auto;
width: 100px;
height: 30px;
display: block;
font-size: 0px;
color: #003261
}
div#oup h1 a:hover {color: #003261}
div#clickableheader h1 a {
margin-top: 20px;
width: 1000px;
height: 200px;
display: block;
font-size:0px;
color: #003261;
}
div#clickableheader h1 a:hover {color: #003261}

/* nav */
#nav {
width: 400px;
margin-left: 0px;
margin-right: auto;
margin-top: -70px;
line-height: 20px;
height: 100px;
text-align: center;
font-size: 12px;}
#nav ul {list-style-type: none;}
#nav li {display: block; float:left; width: 50px; padding: 40px 20px 40px 25px; border: none; background: url("images/DBlueUp.jpg") no-repeat;}
#nav li.page-item-6 {padding: 23px 20px 20px 25px; border: none; background: url("images/PU.jpg") no-repeat;}
#nav li.page-item-6.current_page_item {padding: 23px 20px 20px 25px; border: none; background: url("images/PD.jpg") no-repeat;}
#nav li.current_page_item {border: none; background: url("images/DBD.jpg") no-repeat;}
#nav li.page-item-51 {text-align: center; padding: 20px 25px 20px 20px; border: none; background: url("images/GreenUpCentre.png") no-repeat;}
#nav li.page-item-51 a {text-align: center;}
#nav li.page-item-51.current_page_item {padding: 20px 25px 20px 15px; border: none; background: url("images/GD.jpg") no-repeat;}
/* navright */
#navright {
width: 400px;
margin-left: auto ;
margin-right: 0px ;
margin-top: -110px ;
line-height: 20px;
height: 100px;
text-align:center;
font-size: 12px;}
#navright ul {list-style-type: none;}
#navright li {display: block; float:left; width: 50px; padding: 20px 20px 20px 20px; margin: 5px; border: none; background: url("images/LBU.jpg") no-repeat;}
#navright li.page-item-2 {border: none; background: url("images/OU.jpg") no-repeat;}
#navright li.page-item-2.current_page_item {border: none; background: url("images/OD.jpg") no-repeat;}

#navright li.page-item-48.current_page_item {border: none; background: url("images/LBD.jpg") no-repeat;}
#navright li.page-item-13 {padding: 20px 20px 40px 20px; border: none; background: url("images/contact.jpg") no-repeat;}



div.left-navi-blog
{
width:255px;
margin-right:10px;
float:left;
}

div.left-widget
{
width:255px;
margin-top:40px;
background-color:#ffffff;
padding-top:1px;
padding-bottom:200px;
}

div#leftbarfooter
{
background-color:ffff00;
height:15px;
}

div#rightbarfooter
{
background-image:none;
height:15px;
}
div.center-gauche-area
{
width:755px;
margin-right:10px;
float:left;
margin-top:-50px;
}

div.center-blog
{
width:500px;
margin-right:10px;
float:left;
margin-top:-0px;
}

div.post-title
{
visibility: hidden;
margin:0px;
padding:5px;
height:16px;
background-color:#FFFFFF;
}

div.post-content
{
background-color:#FFFFFF;
margin:0px;
padding:5px;
text-align:center;
border-top:#000000 0px solid;
border-bottom:#000000 0px solid;
}

div.post-meta
{
color:#FFFFFF;
margin:0px;
padding:4px;
height:14px;
margin-bottom:10px;
background-color: #ffffff;
}

div.single-meta
{
border:#444 1px dashed;
padding:2px;
margin:5px;
margin-top:10px;
color:#202D32;
background-color:#B0BDC5;
font-size:10px;
}

div.main-meta
{
border:#ccc 1px dashed;
padding:2px;
margin:5px;
margin-top:10px;
color:#666;
background-color:ddd;
font-size:10px;
}

div.commentblog
{
background-color:#B0BDC5;
margin:0px;
padding:5px;
text-align:center;
border-top:#000000 1px solid;
border-bottom:#000000 0px solid;
}
div.singlecommentborder
{
float:left;
}

div.gravatorblog
{
float:left;
width:70px;
}

div.singlecomment
{
float:left;
width:410px;
}

div.right-navi-blog
{
width:200px;
float:left;
}
div.right-widget
{
margin-top:80px;
width:200px;
background-color:#ffffff;
padding-bottom:4px;
padding-right:5px;
}

div.widget-header
{
color:#000000;
font-weight:bold;
padding-left:10px;
padding-top:3px;
}

div.clear
{
clear: left;
margin: 0;
padding: 0;
height: 0;
line-height: 0;
font-size: 0;
}
div#sharebar
{ margin-right:auto;
margin-left:auto;
margin-bottom:0px;
background:#fff;
height:30px;
padding:25px;
color:#003261;
}
div.ouplegal
{
margin-top:0px;
background:#cbeefe;
height:12px;
text-align:center;
padding:5px;
color:#003261;
font-size:10px;
}
div#footer
{
margin-top:0px;
background:#003261;
height:40px;
text-align:center;
padding-top:20px;
color:white;
font-size:16px;
}
div#footer :link {text-decoration:underline}

/*--------------------textgestaltung--------------------*/
p{
margin:0px;
}
h1,h2,h3,h4,h5,h6{
color:#000000;
margin:0px;
padding:0px;
font-size:11px;
}

acronym, abbr, span.caps {
cursor: help;
}
acronym, abbr {

}
blockquote {

}
blockquote cite {

}

hr {

}


dl{
}
dt{
}
dd{
}
ul
{
margin:0px;
margin-left:12px;
list-style:none;
padding-left:8px;
}
ol{
}
li
{
list-style:square;
margin-top:3px;
padding-top:2px;
padding-bottom:2px;
color:#810000;
}
ul ul{
}
blockquote{
}
blockquote p{
}
code{
}
pre{
}
b, strong,i,em {
}
img{

padding:3px;
margin:2px;
}
address {
}

img.ogtzuq{
border:0px;
color:#3B4D56;
}
/*--------------------linkgestaltung--------------------*/

a {text-decoration:none;
color:#FFFFFF;
}
a:link {
text-decoration:none;
color:#FFFFFF;
}
a:visited {
text-decoration:none;
color:#FFFFFF;
}
a:link:focus{
}
a:link:hover, {
font-weight: bold;
}

.post-content a{
color:#333;
}
.post-content a:link
{
color:#333;
}
.post-content a:visited{ color:#333;
}
.post-content a:link:active,
.post-content a:visited:active{color:#333;
}

#single-meta a{
color:#333;
}
#single-meta a:link
{
color:#333;
}
#single-meta a:visited{ color:#333;
}
#single-meta a:link:active,
#single-meta a:visited:active{color:#333;
}
.commentblog a{
color:#333;
}
.commentblog a:link
{
color:#333;
}
.commentblog a:visited{ color:#333;
}
.commentblog a:link:active,
.commentblog a:visited:active{color:#333;
}
/*--------------------bilder als links--------------------*/
a img{

padding:3px;
margin:2px;
}
a:link img {
}
a:visited img {
}
a:link:active img,
a:visited:active img {
}

a:link:hover img,
a:visited:hover img {
padding:3px;
margin:2px;
}
/*--------------------smilies im text--------------------*/
body img.wp-smiley{
}

/*--------------------der weiterlesen link--------------------*/
.more-link{
}
/*--------------------die seiten wenn es mehrere gibt--------------------*/
p.serif{
}
/*--------------------suche--------------------*/
#searchform{
}
input#s{
}
input#searchsubmit{
}


/*--------------------Kommentare--------------------*/
.alt {

}
.commentlist { padding:0px;
margin:0px;

}

.nocomments {
text-align:center;

}

.commentlist li {
padding:0px;
margin:0px;
list-style:none;
color:#111;

}
.commentlist cite,
.commentlist cite a {

}
.commentlist p {
text-align:center;
padding:0px;
padding-top:5px;

}
#commentform p {

}
.commentmetadata {

}
#commentform input {
border:1px solid #333;
margin-bottom:3px;
}
#commentform textarea {
border:1px solid #333;
width:488px;
}
#commentform #submit {

}
/*--------------------fuer den wp kalender--------------------*/

#wp-calendar th {

}

#wp-calendar {
empty-cells: show;

}
#wp-calendar #next a {

}
#wp-calendar #prev a {

}
#wp-calendar a {

}
#wp-calendar caption {

}
#wp-calendar td {

}
#wp-calendar td.pad:hover {
}

/*-------------------- widgets---------------------*/
h2.widgettitle{
}
.widget {
}
/*--------------------Archive--------------------*/
li#archives{
}
.widget_archives{
}
/*--recent posts--*/

li#recent-posts{
}
.widget_recent_entries{
}

/*--------------------text widget--------------------*/
li.widget_text{
}
/*--id haengt von der nummer des text widgets ab*/
li#text-4{
}
div.textwidget{
}
/*--------------------links blogroll--------------------*/
li#links{
}
.widget_links{
}

/*--------------------kategorien--------------------*/
li#categories{
}
.widget_categories{
}
/*-------------------WP Requires------------------*/
.aligncenter {
display: block;
margin-left: auto;
margin-right: auto;
}
.alignleft {
float: left;
}
.alignright {
float: right;
}
.wp-caption {
border: 1px solid #ddd;
text-align:center;
background-color: #f3f3f3;
padding-top: 4px;
margin: 10px;
-moz-border-radius: 3px;
-khtml-border-radius: 3px;
-webkit-border-radius: 3px;
border-radius: 3px;
}
.wp-caption img {
margin: 0;
padding: 0;
border: 0 none;
}
.wp-caption-dd {
font-size: 11px;
line-height: 17px;
padding: 0 4px 5px;
margin: 0;

}