No the classes are not working because you have nested them within the moz-document url-prefix styles at the bottom of the css file. There should be an extra closing bracket before your new rules.
@-moz-document url-prefix() {
select{
min-width:3em;font-size:.9em;margin-left:.5em;padding:.1em;}
.kern{
letter-spacing:-.1;}
a.download-btn{
padding:3px 12px 2px;}
}/* this was missing */
/*My Feeble CSS*/
Also this is not a valid colour as you have 7 values and hex is only 6 values.
color: #ef84218;
Lastly I don’t understand why you would need the moz-document prefix anyway as you are doing nothing special and if you do need it I would advise you not to use it anyway and find a better way to achieve what you want. Hacking styles right at the start of a project is the worst way to code.