Create 1px thin grey horizontal line under header (menu)

Hi Simon,

Try this CSS:

.site-header {
    border-bottom: 1px solid #000;
}

Adding CSS: https://docs.generatepress.com/article/adding-css/

If this doesn't work, please link me to the page in question.

Thanks!

Hi, Unfortunately, that CSS code doesn't seem to work? See makemesustainable.com

That's likely because you are missing a closing bracket } for your previous CSS:
https://www.screencast.com/t/CZRgOYoNn

Thanks, That's fixed. But the line only seems to appear on Desktop version, not mobile?

Resolved by adding the following:-
.site-header, #mobile-header

Glad to hear :)