Thanks for your reply.
It did not work until I wrote “!important” – but now it Works:
.page-id-523 header#masthead {
display: none !important;
}
.page-id-523 footer#colophon {
display: none;
}
.page-id-523 #main-nav {
display: none; !important;
}
Dont know what “!important” does.
I need to to this for several pages. Is it possible to include more page ids in the CSS i wrote above, so that it looks something like this:
.page-id-523,.page-id-524,.page-id-525 header#masthead {
display: none !important;
}