Center div on page

HTML

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
    
    <head></head>
    
    <body>
        <div id="branchSelect">
             <h4 class="selectBranch">Select a Branch to View</h4>

            <select type="select" id="ddlBranches" class="selectBranch">
                <option id="defaultBranchesListItem" value="0">Select a branch...</option>
                <option value="1">Atlanta</option>
            </select>
        </div>
    </body>

</html>

CSS

div#branchSelect {
    1000px;
    margin: 0 auto;
    width:100px;
}