Css has nothing to do directly with SEO, but you can have more SEO-friendly content for the robots and hide the content with what you want visual visitors to see. For instance, having a logo that's also working as the name of your page or site looks okay to visual visitors, but a blind person or a robot (such as a googliebot) only notes that there is an image and does no see the name of the site. Using CSS image-replacement techniques can allow you to have the text content available for bots while showing people with images-on a nice logo. The example for this is at the bottom of this page: http://www.mezzoblue.com/tests/revised-image-replacement/ But other than using it as a tool to make a semantically-written web page look better without losing information the robots want, CSS has nothing to do with SEO. Good luck.
i think you have wrong tiped your question there. Like the member before CSS doesn.t have to do anything in comon with SEO. Or is not directly related!! trough this relationship..sorry