first
Hypertext links in HTML (draft)
BEGIN or FIRST
The BEGIN relationship identifies the author- defined start of
a sequence of documents of which the current document is a
node. TOP is a functional equivalent to BEGIN when only one of
these values is specified.
When REL=BEGIN, the target document is the beginning of the
sequence. When REV=BEGIN, the current document is the
beginning of the sequence.
If the hypertext link is specified with REL in a LINK element,
an HTML user agent may present an icon in a tool bar.
[引用: 4.4e. Sequence Links -- Hypertext links in HTML (draft) より]