Changing the placeholder text for search field in a Responsive Layout

I wonder if anyone can point me in the right direction to change the default place holder text (-Search-) that's shown in the search field in Responsive Layouts?

I need to translate this text to German. I found the 'localisation' section in the code at the end of the 'search' layout page and made the change there, but this hasn't had any effect.I'm thinking that perhaps I need to 'switch on' localisation somewhere?

Thanks!

Claire