The style sheets can specify how a document is to be presented on different media: on the screen, on paper, speech synthesiser, etc. You can specify that some of the features of your CSS stylesheet should be taken into account only in the oXygen Author and ignored in the rest. This can be accomplished by using the media type oxygen.
For instance using the following CSS:
b{ font-weight:bold; display:inline; } @media oxygen{ b{ text-decoration:underline; } }
would make a text bold if the document was opened in a web browser who does not recognize @media oxygen
and bold and underlined in oXygen Author.
You can use this media type to group specific oXygen CSS features and also to hide them when opening the documents with other viewers.