This code system http://hl7.org/fhir/v3/HtmlLinkType defines the following codes:

CodeDisplayDefinition
alternatealternateDesignates substitute versions for the document in which the link occurs. When used together with the lang attribute, it implies a translated version of the document. When used together with the media attribute, it implies a version designed for a different medium (or media).
appendixappendixRefers to a document serving as an appendix in a collection of documents.
bookmarkbookmarkRefers to a bookmark. A bookmark is a link to a key entry point within an extended document. The title attribute may be used, for example, to label the bookmark. Note that several bookmarks may be defined in each document.
chapterchapterRefers to a document serving as a chapter in a collection of documents.
contentscontentsRefers to a document serving as a table of contents. Some user agents also support the synonym ToC (from "Table of Contents").
copyrightcopyrightRefers to a copyright statement for the current document.
glossaryglossaryRefers to a document providing a glossary of terms that pertain to the current document.
helphelpRefers to a document offering help (more information, links to other sources of information, etc.).
indexindexRefers to a document providing an index for the current document.
nextnextRefers to the next document in a linear sequence of documents. User agents may choose to preload the "next" document, to reduce the perceived load time.
prevprevRefers to the previous document in an ordered series of documents. Some user agents also support the synonym "Previous".
sectionsectionRefers to a document serving as a section in a collection of documents.
startstartRefers to the first document in a collection of documents. This link type tells search engines which document is considered by the author to be the starting point of the collection.
stylesheetstylesheetRefers to an external style sheet. See the section on external style sheets for details. This is used together with the link type "Alternate" for user-selectable alternate style sheets.
subsectionsubsectionRefers to a document serving as a subsection in a collection of documents.