Space between the navbar and the forum
 

Can someone PLEASE tell me how to remove the space between the navbar and the forum?

Or a way to fill it in white, so it doesn't show the background?

Does the same thing happen on a default style with all mods disabled?

Should be:

> AdminCP > Styles & Templates > Style Manager > Edit stylevars > *Look under Navbar stylevars, find "Navigation Bar Margin" and if the bottom vlaue is set to 10, change it to 0 and save.

That should do the trick ;).

It was already at 0!

Add this to additional.css

Then your default style must be from the original 4.x version or a past 4.x default version i.e. if you installed 4.2.1, it installed a default 4.2.1 theme and if you're on 4.2.3, even if it said the templates and such merged correctly it is not in fact a 100% Default 4.2.3 style, follow? That could be your case I'm not sure.

This will work-around the default style issue, add this to additional.css:
Edit: I was still typing Seven :p. Use Seven's method above, it uses !important like mine but his brain said "let's set the above body to 0" which is better than setting the body_wrapper to -10, so use his respectively!