ARIA state for current page in navigation

you may also use aria-current="page" for describing current displayed page among navigation items.

I believe that aria-selected is for 'widgets' that are one-tab stop, like a set of tabs that you then arrow around to select. The selected aspect is about which one is in focus, not which page you are on.

I would check out this as a well tested example: http://whatsock.com/tsg/Coding%20Arena/ARIA%20Menus/Horizontal%20(Internal%20Content)/demo.htm

From: http://whatsock.com/tsg/

For showing the current page I would probably use a more traditional method: Make it not a link. E.g:

<li><a href='page2.php'>Page 2</a></li>
<li><strong>Page 3</strong></li>

This also prevents people from clicking on the same-page link by accident (which I see quite often in usability testing). You can apply the same CSS to nav ul a and nav ul strong and then override the styling for the strong.