spine
Lists the core elements of the eBook in the reading order in which they appear in the final .lit file. This does not include out-of-spine content.

Typically, this lists the body file or a sequence of chapter files. If more than one file is listed in the spine, the .htm files are concatenated in the order presented. If chapter 10 is listed here before chapter 2, it will appear in that sequence in the final Reader format file as well.

attributes

id
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.
class
Affiliates an element with one or more classes.
style
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".

See also:

<itemref>