I encountered this strange thing:
My website is http://www.yisee.org
I have a CSS style file Geshi.css
because the web pages didn't show as planned, I downloaded the entire page to desktop for analysizing.
Then I found this:

This Geshi.css file on the server side has this content:

#nav0 #container #nav #nav00 a,
#nav1 #container #nav #nav01 a,
#nav2 #container #nav #nav02 a,
#nav3 #container #nav #nav03 a,
#nav4 #container #nav #nav04 a,
#nav5 #container #nav #nav05 a,
#nav6 #container #nav #nav06 a,
#nav7 #container #nav #nav07 a,
#nav8 #container #nav #nav08 a,
#nav9 #container #nav #nav09 a,
#na10 #container #nav #nav10 a,
#na11 #container #nav #nav11 a,{color:gold; background:url(00Comm/red.jpg);}

but the downloaded Geshi.css file doesn't have this content.

What caused this problem, how can I fix it?

by try and correct, I solved this problem by adding a body before the sign #, like this:

body#nav0 #container #nav #nav00 a,
body#nav1 #container #nav #nav01 a,
body#nav2 #container #nav #nav02 a,
body#nav3 #container #nav #nav03 a,
body#nav4 #container #nav #nav04 a,
body#nav5 #container #nav #nav05 a,
body#nav6 #container #nav #nav06 a,
body#nav7 #container #nav #nav07 a,
body#nav8 #container #nav #nav08 a,
body#nav9 #container #nav #nav09 a,
body#na10 #container #nav #nav10 a,
body#na11 #container #nav #nav11 a,{color:gold; background:url(00Comm/red.jpg);}

But my intention of highlighting current page with css still can't be realized, although it worked quite good on the simulator.

Can anybody tell me how to highlight current page with css on this server?
Is there ay success story to share?
Thank you!

My primary purpose is to highlight the current page.
Since the html css combination doesn't solve this problem, I turned to php "if...else" clause, and solved it.