Squirrely menu on post view

On normal viewing of my blog page, the menu sits nicely at the left like I tell it to – but if I view a particular post, then it jumps into the main text section! Why? Can anyone tell me what I’m doing wrong? I’ve spent hours trying to figure it out myself (very new at css). Thank you! Nancy

My css file looks like this:

‘/*
Template: zen-min
Theme Name: Zen Minimalist
Description: Imageless style using a tabbed horizontal menu
Author: Joni Mueller
Author URI: http://www.webjones.org

Credit goes to Root of http://www.atthe404.com for his Odyssey interface and Gemini template
Zen-Min CSS Design by Joni Mueller http://www.webjones.org/
Tabbed Menu for WP Pages from technique found at http://css.maxdesign.com.au/listamatic/
*/

a {
color: #666;
text-decoration:none;
}

a img {
border: none;
}

#content a img {
border: none;
padding: 0px;
margin: 0px;
}

a:visited {
color: #666;
}

a:hover {
color: #FF0000;
}

acronym, abbr {
border-bottom: 1px dashed #333;
}

acronym, abbr, span.caps {
cursor: help;
font-size: 11px;
letter-spacing: .07em;
}

blockquote {
border-left: 5px solid #ccc;
margin-left: 1.5em;
padding-left: 5px;
}

body {
background: #fff;
font-family: “Lucida Grande”, “Lucida Sans Unicode”, “Trebuchet MS”, Verdana, Helvetica, sans-serif;
font-size: 11px;
color: #333;
text-transform: lowercase;
margin: 0;
padding: 0;
text-align: center; /* IE 5.5 hack */
}

cite {
font-size: 10px;
font-style: normal;
}

h1 {
margin: 25px 10px 20px 0px;
padding: 0px;
text-align: left;
}

h2 {
font-size: 13px;
font-weight: normal;
margin: 15px 20px 0 25px;
padding-bottom: 2px;
}

h3 {
font-size: 20px;
font-weight: normal;
margin-top: 0;
padding-bottom: 0;
}

h1 a:hover, h2 a:hover, h3 a:hover {
color: #c00;
}

ol#comments li p {
font-size: 100%;
}

p, li, .feedback {
font-size: 13px;
}

ul.post-meta {
list-style: none;
}

ul.post-meta span.post-meta-key {
font-weight: bold;
}

.credit {
background: #fff;
color: #000;
font-size: 11px;
margin: 10px 0 0 0;
padding: 3px;
text-align: center;
}

.credit a:link, .credit a:hover {
color: #c00;
text-decoration: none;
}

.feedback {
color: #ccc;
text-align: left;
clear: both;
font-size: 90%;
}

.floatleft
{
float: left;
margin: 10px 10px 10px 0;
border: 0px solid #666;
padding: 5px;
}

.floatright
{
float: right;
margin: 10px 0 10px 10px;
border: 0px solid #666;
padding: 5px;
}

.meta {
font-size: 90%;
}

.meta li, ul.post-meta li {
display: inline;
}

.meta ul {
display: inline;
list-style: none;
margin: 0;
padding: 0;
}

.meta, .meta a {
color: #009;
font-weight: normal;
letter-spacing: 0;
}

.post, #comments-post {
margin-top: 5px;
margin-right: 25px;
margin-left: 25px;
margin-bottom: 35px;
}

.storytitle {
margin-top: 10px;
margin-bottom: 2px;
}

.storytitle a {
text-decoration: none;
color: #000000
}

.storycontent a {
color: #00008B;
border-bottom: dotted 1px #00008B;
}

.storycontent a:hover {
color: #FF0000;
border-bottom: solid 1px #FF0000;
}

.trackback { font-size: 12px; text-align: center; }

.textarea {
width: 200px;
margin: 0;
}

#clearer {
clear: both;
margin: 0;
padding: 0;
}

#commentform #comment{
width: 450px;
margin: 0;
padding: 10px;
}

#commentform #author, #commentform #email, #commentform #url, #commentform textarea {
background: #eee;
color: #333;
border: 1px solid #333;
padding: .2em;
}

#commentform textarea {
width: 100%;
}

#commentlist li ul {
border-left: 3px solid #eee;
font-size: 12px;
list-style-type: none;
}
#content {
float: left;
width: 67%;
border: 1px solid #000;
margin: 0px;
padding: 0px;
background-color: #fff;
}

#footer {
border-top: 1px solid #ccc;
margin-bottom: 0;
margin-left: 30px;
margin-right: 30px;
}

#main {
}

#header, #header a:link {
font-size: 20px;
font-weight: normal;
color: #ccc;
text-decoration: none;
}

#header a:hover {
color: #c00;
}

#menu {
float: left;
width: 180px;
margin: 0 0 0 15px;

}

#nav {
padding-left: 3px;
padding-right: 0px;
}

#nav form {
margin: 0 0 0 13px;
}

#nav input#s {
width: 80%;
background: #eee;
border: 1px solid #333;
color: #000;
}

#nav ul {
color: #333;
font-weight: normal;
font-size: 18px;
list-style-type: none;
margin: 0;
padding-left: 0px;
text-transform: lowercase;
}

/* this is a fix for the way WP handles styling for link and theme switcher */
#nav li h2 {
color: #333;
font-weight: normal;
font-size: 16px;
list-style-type: none;
margin: 0;
padding-left: 0px;
text-transform: lowercase;
}

#nav ul li {
font-size: 16px;
margin-top: 10px;
padding-bottom: 2px; /*border-bottom: dotted 1px #ccc;*/
}

#nav ul ul {
font-size: 12px;
font-weight: normal;
line-height: normal;
list-style-type: none;
margin: 0;
padding: 0;
text-align: left;
}

#nav ul ul li, #nav ul li ul li {
font-size: 12px;
font-weight: normal;
border: 0;
letter-spacing: 0;
margin-top: 0;
padding-left: 10px;
}

#nav ul ul li a {
color: #444;
text-decoration: none;
}

#nav ul ul li a:hover {
border-bottom: 1px solid #333;
}

#nav ul ul ul.children {
font-size: 11px;
padding-left: 10px;
}

#rap {
width: 80%;
background: #fff;
margin: auto;
text-align: left; /* IE 5.5 hack part II */
}
#wp-calendar {
border: 1px solid #000;
empty-cells: show;
font-size: 11px;
margin: 0;
width: 95%;
text-align: center;
}

#wp-calendar #next a {
padding-right: 10px;
text-align: right;
}

#wp-calendar #prev a {
padding-left: 10px;
text-align: left;
}

#wp-calendar a {
display: block;
text-decoration: none;
}

#wp-calendar a:hover {
background: #eee;
color: #333;
}

#wp-calendar caption {
color: #444;
font-size: 18px;
font-weight: normal;
text-align: right;
}

#wp-calendar td {
color: #444;
font-weight: normal;
font-size: 11px;
letter-spacing: normal;
padding: 2px 0;
text-align: center;
}

#wp-calendar td.pad:hover {
background: #fff;
}

#wp-calendar td:hover, #wp-calendar #today {
background: #eee;
color: #000;
}

#wp-calendar th {
font-style: normal;
text-transform: capitalize;
}

/* tabbed navigation code */

#pagetab {
padding: 5px 0 3px 0;
margin: 10px 0 0 1px;
font-weight: bold;
font-size: 10px;
font-family: arial, “Trebuchet MS”, sans-serif;
}

#pagetab ul {
list-style: none;
margin: 0;
display: inline;
}

#pagetab li {
list-style: none;
margin: 0;
display: inline;
}

#pagetab li a {
padding: 3px 0.5em;
margin-left: 1px;
border: 1px solid #777;
border-bottom: none;
background: #ccc;
text-decoration: none;
}

#pagetab li a:link { color: #444; }

#pagetab li a:visited { color: #666; }

#pagetab li a:hover {
color: #c00;
background: #fff;
border-top: 1px solid #222;
border-right: 1px solid #222;
border-bottom: 1px solid #fff !important;
border-left: 1px solid #222;
}

#pagetab li a#current {
background: #fff;
border-bottom: none;
}

.page_item {
margin: 0;
padding: 0;
}’