Never put css style definitions inside your template. Always add css to the page where you have the CN include code.
more information:
Well this isn't that difficult. All you need to know is that Cutenews sends back html only to a browser. So on the server the CN include code is replaced by the html of the articles (templates). If you understand this then it's just a matter of using css like you do for other components on your webpage.
Add the css classes to your stylesheet /<style> tags and inside the templates you make reference to the css classes like