[development] Deployment process

Hello all very early on in my Drupal learning process but have been asked to come up with a solution where the client will be entering content on the production site and we may very well be making structural changes ( css etc ) on DEV and changes to the site setup ( for example a page name or somesuch ) , is there a way to seperate the data entered for content types from everything else so when deploying a site to production we can do so without worrying about content being lost. Thanks Stewart http://www.flickr.com/people/mrbirch