I see that the About Us link in your menu links to http://aswatngo.com/about. Did you publish a page with the URL aswatngo.com/about or just enter that URL in the menu builder? It looks like you haven't published a page with that URL yet. That's why you get 404 Page Not Found Error when you click on the link.
The URL for each of your pages must match the URLs in your menu exactly.