There's a few unneccesary usages of -moz CSS, and some CSS that doesn't use the -moz prefix, but does use the -moz specific syntax and so probably doesn't do anything at the moment.

mod/chat/gui_ajax/theme/bubble/chat.css
13:#input-message

{background:#FFFFFF url(input.png) repeat-x scroll 0 0;padding:0 9px;border: 1px solid #999;border-radius: 9px;-moz-border-radius: 9px;}

63: -moz-border-radius:10px;

mod/chat/gui_ajax/theme/compact/chat.css
19: -moz-border-radius-topleft: 6px;
20: -moz-border-radius-topright: 6px;
28: -moz-border-radius-bottomleft: 6px;
29: -moz-border-radius-bottomright: 6px;
40: -moz-border-radius-bottomleft: 6px;
41: -moz-border-radius-bottomright: 6px;

admin/tool/health/styles.css
6: -moz-border-radius: 6px;

mod/chat/gui_ajax/theme/compact/chat.css
28: -moz-border-radius-bottomleft: 6px;
40: -moz-border-radius-bottomleft: 6px;

mod/quiz/styles.css
681: border-radius-bottomleft: 0;
769: border-radius-bottomleft: 0;
896: border-radius-bottomleft: 0;
914: border-radius-bottomleft: 0;
937: border-radius-bottomleft: 0;

If it's okay I'll reformat and clean up a couple of other things in the chat.css files at the same time.