Question

I am validating against html5 and I know that the validator is not 100% but it even shows it should allow this in it’s suggestion…

Ouptut:

Line 75, Column 92: Bad value home for attribute rel on element a:
Keyword home is not registered.

…bomb/" rel="home" title="beefbomb.com"><img src="http://localhost/local_folder…

It then tells me to take a look at the microformats wiki… http://microformats.org/wiki/existing-rel-values#HTML5_link_type_extensions

Which defines:

Keyword: home

Effect on a, area: Hyperlink

Brief description: …indicates that the [referenced document] is
the homepage of the site in which the current page appears. can be
combined with ‘alternate’ to indicate for example a feed for the site
of the current page.

Link to specification: rel-home

Why could this be?

Answer 1

Microformats aren’t part of the official spec. A future ua could come along that decides to treat links with rel=”home” on them as links to go to the homescreen of the device for instance, without going against the spec.

The warning is to ask you, “Have you done this for a reason, or by mistake?”. If you know what you are doing and why, it’s fine. If you decided to make up a new rel attribute for your own reasons, you get told that it’s not in spec, but that a system already exists that uses it.