I've done some branding to IG 2.5.1 with a custom.css file.

For example I've changed the color of the .headerbrand element.
It works fine.

But if I resize the browser window so it gets smaller it loads a
client.narrow.css that changes back the .headerbrand style to the
settings that are specified in client.narrow.css, overwriting the color
from custom.css

Any tips on how I can make custom.css the default?