Every Creative Commons license has three layers: the lawyer-readable legal code, the human-readable deed, and the machine-readable code. As the only legally-operative layer, the legal code is the primary layer of the CC licenses. It consists of the text of the licenses, as well as any meaningful formatting and other inseparable elements listed below.
Anything not specifically named as legal code above, including:
"HTML and other coding that does not change the user's view of legal code elements
CC has committed to maintaining the legal code of its licenses completely unchanged after publication. Licensors and licensees can depend on the text remaining static, and do not have to check back to see if anything has changed.
Any change to the legal code itself requires CC to release a new version. Small errors may remain in the legal code and be noted as errata; these may be found separately on the errata page or otherwise maintained separately from the main legal code.
Elements of the license page that are not legal code may be changed by CC in its discretion. For example, the disclaimer text may be altered, inter-language links included, or explanatory non-license text added.
The legal code is currently maintained as part of the HTML files that are displayed, where the legal code itself is mixed in with non-legal elements such as stylistic display information and additional text. There does not currently (as of September 2013) exist a file with a canonical version of the legal code without the non-legal code elements of that page, such as the navigational and stylistic elements.
There are proposals to maintain a canonical version of the legal code only, which have been set aside to be reconsidered sometime after the launch of 4.0. One presentation of this idea by CC staff is posted here.