Firefox UI help

How do I get rid of this white line?
I've already used this and it removes one line of pixel but stills still another line of pixel.
#navigator-toolbox::after {
display: none !important;
}
I'm also using classic theme restorer Firefox addon.
Comments
#main-window toolbar {
background: none !important;
border: none !important;
box-shadow: none !important;
}
EDIT: nope, it's #navigator-toolbox:after, works here fine (BTW, i took the code from the Fx default file). Make it border-bottom: 4px solid red and see it:
That white line of pixel still there
Alternatively, play with the margin code from the CTR source file.
(C&P)