Header overlay

Hi there,

please can you tell me why on some pages of the site I’m making I see the semi-transparent white header behind the logo and navigation and others I don’t?

For example:

The page here has it: http://www.palatin.no/om-oss/
but the page here does not: http://www.palatin.no/kurs/forhandlinger/

I would like it on all my pages?

Please can you advise?

Many thanks