Trying to add Expandable Search bar in header

[phillycheese123]

I would like to edit either the search sidebox or the search header css to make it expand when clicked inside ....like so http://www.cibgraphics.com/blog/arti...le_search_form

my problem is the only css i can find for the search bar is

#navMainSearch { }

all the styling is controlled within the php.

Is there someway of having the style controlled within the css so that i can add the behaviour im talking about?

Thanks for your help, Zencart is the sh@it

edit**my bad form,select, input is in the css but that is general..affecting more than the search bar
-Phil