<div data-bind="page: {id: 'start'}">
    <a href="#user/fry">Go to Fry</a>
</div>

<div data-bind="page: {id: 'user'}">
    User:
    <!-- {1} will be replaced with whatever matched the wildcard -->
    <div data-bind="page: {id: '?', sourceOnShow: 'user/{1}.html'}">
    </div>
</div>