http://oxtis.com/ProjectX/

as you can see in the link provided.
the sides of the content is smaller than the header and the footer.
what is wrong ?

Code:
body {
    margin:0px;
    padding:0px;
    font-family: 'Dosis', sans-serif;
    background-color: #98a0a5;
    color: #bdc8d7;
}

#header{
    width: 900px;
    margin: 0px auto 0px auto;
    border: 1px solid #000;
    clear: both;
}

#navbar {
    width: 900px;
    margin: 0px auto 0px auto;
    border: 1px solid #070b0e;
    background: #304052;
}

#content {
    width: 900px;
    margin: 0px auto 0px auto;
    clear: both;
}

#contentleft {
    width: 598px;
    float: left;
    border: 1px solid #070b0e;
    background: #10151b;
}

#sidebar {
    width: 298px;
    float: right;
    border: 1px solid #070b0e;
    background: #10151b;
}

#footer {
    width: 900px;
    margin: 0px auto 0px auto;
    border: 1px solid #000;
    clear: both;
    background: #1b222c;
    text-align: center;
}