XSL and CSS Together

XSL goes a few steps beyond CSSin applying styles to generations of elements: 

It can also create new document contents and perform sophisticated selection techniques.

Although CSS does not have an effect on this type of data, XSL can.So, you can use XSL and CDD together for two purposes:

Use XSL to transform information,

Style information with CSS

Online reference: http://w3.org/TR/NOTE-XSL-and-CSS

Official XSL page:  http://www.w3.org/Style/XSL/