Edit margin/padding of a menu item / module

Hi,

I added a login box to the menu using the [modid=xxx] code
The login box displays ok but it has the same margin/padding as all the other buttons.
Can I edit the margin/padding around that button only?

I tried to edit it in the module's settings.

Hi
yes you can do that using some custom css rules (I assume that you don't have the maximenu params as you are using the code [modid XX])
Each menu item has a unique CSS class that you can point with CSS
CEd

Is there anywhere I can see a list of these css rules,
I often wonder how to use that feature in joomla.

you must use the Firebug tool (or any other developer tool in your browser)
it will allow you to see all the classes, test your code, and many more

the CSS are not specific to joomla, if you give me your url I can help you