How to remove hide the select arrow in Firefox using

-moz-appearance:none;

More info and background:

Check this cheesy gist for the full story.

It's as hacky simple as:

1. Set

   -prefix-appearance

   to none to remove the styles;
2. Use

   text-indent

   to "push" the content a bit to the right;
3. Finally, set

   text-overflow

   to an empty string. Everything that extends beyond it's width will become... nothing! And that includes the arrow.

Brought to you by @joaocunha

Follow the guy!