I have found where you inside fckconfig.js can declare custom formats that will show in the html file like style="" attributes

FCKConfig.CustomStyles =
{
    'Red Title'    : { Element : 'h3', Styles : { 'color' : 'Red' } },
    'White Title'    : { Element : 'h3', Styles : { 'color' : 'white','font-family' : 'Trebuchet MS' } },
    'White paragraph'    : { Element : 'P', Styles : { 'color' : 'white','font-family' : 'Trebuchet MS','font-weight' : 'bold' } }
};

but I am looking for the place in the fckcustom where you declare your custom css classes?

is it under "List of available styles for the editor" or under "Edito area css" you add your custom css classes?

and added to that there is an option "style list generation mode" [Static | Dynamic | Url] which does seme to work the way I want to

under "Edito area css" it says the similar "CSS generator mode" with the same options [Static | Dynamic | Url] ?

have been playing around with these settings but it seems very hard to make it work in an easy way?