I've finally figured out how to change the message pane and folder pane fonts, with the code below in userchrome.css. However, if I increase the message pane font beyond 9 pt, the rows start to overlap, because the font size increases but the line-spacing doesn't. Can anyone suggest how I'd fix this, either so the space is scaled with the font, or I just specify it in the code below? Thanks.
/* Change Browser Fonts */
* { font-size: 8pt !important;
font-family: Verdana !important; }
/* Folderpane(color/text) & Messagepane(color) */
treechildren {
background-color: #F1F1F1 !important;
font-family: Verdana !important;
font-size: 14px !important; }
/* Messagepane text */
treechildren:-moz-tree-cell-text(unread) {
font-size: 9pt !important;
font-family : Arial bold !important}
treechildren:-moz-tree-cell-text(read) {
font-size: 9pt ! important;
font-family : Arial !important; }