When -L is turned on, only the relative links are ever followed. Relative links are here defined those that do not refer to the web server root. For example, these links are relative:
<a href="foo.gif">
<a href="foo/bar.gif">
<a href="../foo/bar.gif">
These links are not relative:
<a href="/foo.gif">
<a href="/foo/bar.gif">
<a href="http://www.server.com/foo/bar.gif">
Using this option guarantees that recursive retrieval will not span hosts, even without -H. In simple cases it also allows downloads to “just work” without having to convert links.
This option is probably not very useful and might be removed in a future release.