Firefox Navbar displaying incorrectly

I completed a website this week in BSS, but the Navbar is not showing correctly on Firefox 77.0.1 It looks as it should on other browsers: http://www.seefunding.co.uk/ Any ideas

It's because you have the fluid class applied to your header image, which sets the width to 100%, so it's taking up the entire width of the header. Deselect the fluid box and set a fixed width on the image or its parent container.

Thanks, lifesaver!