Are you using Dreamweavers option to check files in and out?
If so, make sure the CSS File is checked out before using CSS Sculptor to make any changes.
Do you have other CSS That is overriding the change you made?
try stripping out any additional CSS you may have added.
Also, make that the CSS File was uploaded to the server and that you are not viewing a cached copy of the page. You can try using another browser or doing a Hard Refresh. on Windows in FireFox,a Hard Refresh is done using the ctrl+F5 key.