flex4 superTabNavigator 的图标有关问题

flex4 superTabNavigator 的图标问题
<fx:Style>
@namespace supertabs "flexlib.controls.tabBarClasses.*";

supertabs|SuperTab
{
tabCloseButtonStyleName: "closeButton";
}
.closeButton
{
upSkin:Embed(source="assets/assets.swf", symbol="firefox_close_up");
downSkin:Embed(source="assets/assets.swf", symbol="firefox_close_down");
overSkin:Embed(source="assets/assets.swf", symbol="firefox_close_over");
}

</fx:Style>