changing the tree background color (only affects linux): in gtk2, unfocused selected row weren't visible because they had the same background color as the trees.

toolkit/skin/win/tree.css

@@ -36,8 +36,8 @@ tree {
   -moz-border-right-colors: ThreeDHighlight ThreeDLightShadow;
   -moz-border-bottom-colors: ThreeDHighlight ThreeDLightShadow;
   -moz-border-left-colors: ThreeDShadow ThreeDDarkShadow;
-  background-color: Window;
+  background-color: -moz-Field;
-  color: WindowText;
+  color: -moz-FieldText;
   -moz-appearance: listbox;
 }