Cannot remove outline/dotted border from Firefox select drop down [duplicate]
Solution 1:
Found my answer here: https://stackoverflow.com/a/18853002/1261316
It wasn't set as the correct answer, but it worked perfectly for me:
select:-moz-focusring {
color: transparent;
text-shadow: 0 0 0 #000;
}
select {
background: transparent;
}