Getting more complex now you are into the detail. Partly, things depend upon the laws applicable in a given instance. In some cases copyright has to be explicitly claimed and in other jurisdictions it is implicit. This has been touched on at HN before - CSS code (and JavaScript, HTML etc) is effectively open in that it is generally available to be read by all but it may still be 'owned' in the sense that copyright will often still apply.
Perhaps one should apply a 'moral' filter. It seems OK (if not inevitable) for one's designs to be strongly influenced by the layout and colour schemes of existing sites but it also seems proper that one should not copy CSS and layouts wholesale from elsewhere. There are plenty of tutorial sites demonstrating the most complex of CSS code - copy from them where it encouraged and then apply your own unique 'spin'.
Perhaps one should apply a 'moral' filter. It seems OK (if not inevitable) for one's designs to be strongly influenced by the layout and colour schemes of existing sites but it also seems proper that one should not copy CSS and layouts wholesale from elsewhere. There are plenty of tutorial sites demonstrating the most complex of CSS code - copy from them where it encouraged and then apply your own unique 'spin'.