A slight question – you say CSS is designed to show the page? To me this would be more PHP that would be doing this auto placing of the page. Would it be possible to paste in what code (if you know it) does this in your navigation please. Be good to see what the calls are.
Just adding to that because I apparently can’t edit…
If by selected you mean ‘on state’ as in on that page then it would be a classname like this:
#nav li.current_page_item a
Do you have current_page_item anywhere in your CSS?
Beggar can never be bankrupt.
It is with our passions, as it is with fire and water, they are good servants but bad masters