Menu Item align Right

Hello,

Trying to configure one or two of my menu items to align right instead of left with the others.

Google brought me to a couple of forums suggesting style.css editing as follows:
Find the “menu-item” number for the element in the Menu I wish to “float right” then put the following line in the style.css:

#header-menu-wrap #menu-item-717 {
float: right;
}

or

#menu-item-717 {
float: right;
}

…one problem I encountered is that what looks like the same item in the style.css of the two sites installations I run under my Network, corresponds to two different “numbers”.
I think it is because I use “Custom Menus” instead of the default one for both.

So I went to the editing page of each site and I can’t seem to find a style.css to modify there. It is only available at Network admin level.

When I apply those .css changes at Network admin level, nothing happens…

Is there some other way to accomplish this?

Thank You!