Untitled

.nav {
    width: 100%;
    height: 84px;
    float: left;
    background: #333;

    min-width: 960px; /* or whatever width you need */
}

<html>
    <head>
        <style>
        body { text-align: center; }
        #container { width: 960px; margin: 0 auto; }
        #nav { overflow: hidden; list-style: none; padding: 0; margin: 0; background: #333; }
        #nav li { float: right; }
        #nav li.logo { float: left; }
        #nav li a { display: block; padding: 0px 22px; color:#FFF; background: #333; text-align:center; line-height:84px; font-family: 'open_sansbold'; font-size:80%; }
        #nav li.logo a { width: 317px; height: 84px; background:url('img/lifesign.png') red; }
        </style>
    </head>
    <body>
        <div id="container">
            <ul id="nav">
                <li class="logo"><a href="home.htm"></a></li>
                <li><a href="contact.htm">CONTACT</a></li>
                <li><a href="contact.htm">GET INVOLVED</a></li>
                <li><a href="contact.htm">Q+A</a></li>
                <li><a href="contact.htm">HOW IT WORKS</a></li>
                <li><a href="contact.htm">WHO WE ARE</a></li>
            </ul>
            <div id="main">
                <!-- page content here -->
            </div>
        </div>
    </body>
</html>