Problem with resolution / browsers

Hey, Everything was going good with my website until i sent the url link to a friend who was using a smaller resolution to me (mine is 1400 x 900) and suddenly things got complicated.

I cant seem to figure out how to make it so the site is able to be used in different browsers and also different resolutions.

here is my css code:

[CODE]body {
margin:0px; padding:0px;
background-color:#003333;
font-family:Arial, Helvetica, sans-serif;
}
#bar{
background:url(images/background_slice.jpg) repeat-x #000000;
}
#container{
background:url(images/background_main.jpg) no-repeat;
min-height:800px;
width:1000px;
position:center;
}
body {
margin:50px 0px; padding:0px;
text-align:center;
}

#Content {
width:500px;
margin:0px auto;
text-align:left;
padding:15px;
border:1px dashed #333;
background-color:#eee;
}

/*
Menu / Banner Positioning
*/

#banner { position:absolute; top:134px; left:183px; }

ul#menu {
margin:0px; padding:0px;
position:absolute; top:110px; left:194px;
}

ul#menu li{
margin:0px; padding:0px;
list-style:none;
margin-right:10px;
font-size:12px;
font-family: Arial;
text-transform:uppercase;
display:inline;
}
ul#menu li a{
text-decoration:none;
color:#cc9900;
}
ul#menu li a:hover {
text-decoration:none;
color:#ffffff;
}
body {
margin:0px; padding:0px;
background-color:#11090a;
font-family:Arial, Helvetica, sans-serif;
}
#outside_container {
background:url(images/background_slice.jpg) repeat-x #ffffff;
}
#container {
background:url(images/background_main.jpg) no-repeat;
min-height:800px;
}
/*
Footer
*/
#footer {
border-top:0px solid #000000;
padding:28px 48px 50px 50px;
color:#666666;
font-size:12px;
line-height:15px;
}
#footer img {
float:left;
margin-right:10px;
}
#footer span {
display:block;
float:left;
width:250px;
}
#footer a {
color:#000000;
text-decoration:none;
}
#footer a:hover { color:#666666;
}
/*
Content
*/
#content {
padding-top:420px;
padding-left:360px;
width:815px;
color:#000000;
font-size:13px;
line-height:20px;
text-align: center;

}
.column1 { float:left; width:360px; margin-right:30px; }

[/CODE]

Anyone got any ideas? cheers in advance

Also in #CSS _↴