background image help

hey if anyone could give me some help on how to insert a background image into the header region of bluemarine it would be greatly appreciated

here is style.css

/*
** Page layout blocks / IDs
*/
#header, #content {
width: 900px;
border: 0px solid #FFFFFF;
margin: auto;
}
#header {
background-image: url ('bg10oct1.png');
height: 100px;
}

#logo {
vertical-align: middle;
border: 0;
}
#logo img {
float: left;
padding: 0 1em;
border: 0;
}
#menu {
padding: 0.5em 0.5em 0 0.5em;
text-align: right;
vertical-align: middle;
}
#navlist {
font-size: 1.0em;
padding: 0 0.8em 1.2em 0;
color: #9cf;
}
#navlist a {
font-weight: bold;
color: #fff;
}
#subnavlist {
padding: 0.5em 1.2em 0.4em 0;
font-size: 0.8em;
color: #9cf;
}
#subnavlist a {
font-weight: bold;
color: #9cf;
}
ul.links li {
border-left: 1px solid #9cf;
}
ul.links li.first {
border: none;
}
#search .form-text, #search .form-submit {
border: 1px solid #369;
font-size: 1.1em;
height: 1.5em;
vertical-align: middle;
}
#search .form-text {
width: 8em;
padding: 0 0.5em;
}
#mission {
background-color: #369;
padding: 1.5em 2em;
color: #fff;
}
#mission a, #mission a:visited {
color: #9cf;
font-weight: bold;
}
.site-name {
margin: 0.6em 0 0 0;
padding: 0;
font-size: 2em;
}
.site-name a:link, .site-name a:visited {
color: #fff;
}
.site-name a:hover {
color: #369;
text-decoration: none;
}
.site-slogan {
font-size: 1em;
color: #eee;
display: block;
margin: 0;
font-style: italic;
font-weight: bold;
}
#main {
/* padding in px not ex because IE messes up 100% width tables otherwise */
padding: 10px;
}
#mission, .node .content, .comment .content {
line-height: 1.4em;
}
#help {
font-size: 0.9em;
margin-bottom: 1em;
}
.breadcrumb {
margin-bottom: .5em;
}
.messages {
background-color: #eee;
border: 1px solid #ccc;
padding: 0.3em;
margin-bottom: 1em;
}
.error {
border-color: red;
}
#sidebar-left, #sidebar-right {
background-color: #eee;
width: 155px;
/* padding in px not ex because IE messes up 100% width tables otherwise */
padding: 5px;
vertical-align: top;
}
#footer {
background-color: #eee;
padding: 1em;
font-size: 0.8em;
}

#block-block-4 {
width: 160px;
background: #ffffff;
border: 1px solid #000000;
}

#block-menu-46 {
background: #ffffff;
border: 1 solid #000000;
}

/*
** Common declarations for child classes of node, comment, block, box, etc.
** If you want any of them styled differently for a specific parent, add
** additional rules /with only the differing properties!/ to .parent .class.
** See .comment .title for an example.
*/
.title, .title a {
font-weight: bold;
font-size: 1.3em;
color: #777;
margin: 0 auto; /* decrease default margins for h.title */
}
.submitted {
color: #999;
font-size: 0.8em;
}
.links {
color: #999;
}
.links a {
font-weight: bold;
}
.block, .box {
padding: 0 0 1.5em 0;
}
.block {
border-bottom: 1px solid #bbb;
padding-bottom: 0.75em;
margin-bottom: 1.5em;
}
.block .title {
margin-bottom: .25em;
}
.box .title {
font-size: 1.1em;
}
.node {
margin: .5em 0 2em 0;
}
.sticky {
padding: .5em;
background-color: #eee;
border: solid 1px #ddd;
}
.node .content, .comment .content {
margin: .5em 0 .5em 0;
}
.node .taxonomy {
color: #999;
font-size: 0.8em;
padding-left: 1.5em;
}
.node .picture {
border: 1px solid #ddd;
float: right;
margin: 0.5em;
}
.comment {
border: 1px solid #abc;
padding: .5em;
margin-bottom: 1em;
}
.comment .title a {
font-size: 1.1em;
font-weight: normal;
}
.comment .new {
text-align: right;
font-weight: bold;
font-size: 0.8em;
float: right;
color: red;
}
.comment .picture {
border: 1px solid #abc;
float: right;
margin: 0.5em;
}

/*
** Module specific styles
*/
#aggregator .feed-source {
background-color: #eee;
border: 1px solid #ccc;
padding: 1em;
margin: 1em 0;
}
#aggregator .news-item .categories, #aggregator .source, #aggregator .age {
color: #999;
font-style: italic;
font-size: 0.9em;
}
#aggregator .title {
margin-bottom: 0.5em;
font-size: 1em;
}
#aggregator h3 {
margin-top: 1em;
}
#forum table {
width: 100%;
}
#forum td {
padding: 0.5em;
}
#forum td.forum, #forum td.posts {
background-color: #eee;
}
#forum td.topics, #forum td.last-reply {
background-color: #ddd;
}
#forum td.container {
background-color: #ccc;
}
#forum td.container a {
color: #555;
}
#forum td.statistics, #forum td.settings, #forum td.pager {
height: 1.5em;
border: 1px solid #bbb;
}
#forum td .name {
color: #96c;
}
#forum td .links {
padding-top: 0.7em;
font-size: 0.9em;
}
#profile .profile {
clear: both;
border: 1px solid #abc;
padding: .5em;
margin: 1em 0em;
}
#profile .profile .name {
padding-bottom: 0.5em;
}
.block-forum h3 {
margin-bottom: .5em;
}
div.admin-panel .description {
color: #999;
}
div.admin-panel .body {
background: #f4f4f4;
}
div.admin-panel h3 {
background-color: #69c;
color: #fff;
padding: 5px 8px 5px;
margin: 0;
}