The link/button text more specifically, are those which starts with (non case sesitive) "Next", "Prev", "Previous";
or ends with "Prev", "Back", "Previous", "Next". e.g. "Next", "> Next", "Next Page", "Prev", "< Prev", "< Previous", etc.
but not "< Prev Page" because the word "prev" or "previous" is not at the start/end of text.
This script doesn't take into account of links whose contents is an image rather than text, or whose text is a CSS text contents.
If next/previous navigation link is specified in the HTML metadata, it will be used as a priority.