The <guide> section of the Open eBook package file determines which elements appear on the first page of an eBook:
The <guide> supports only a small group of possible id types and elements derived from the OEB standard.
Provides an element with a unique name within a single document. This is especially useful in works with extensive cross-referencing and linking, such as dictionaries, encyclopedias, or travel guides. Use of ids simplifies linking and updates.
Affiliates an element with one or more classes.
Attaches a list of inline (name:value paired) CSS properties to a specific tag, for example: style="name:value;name:value"
Note: Media types other than "text/x-oeb1-css" will be ignored with a warning in a document of type "text/x-oeb1-document".