I receive this W3C Validation error every time I use Lightbox 2:

Line 196, Column 104: Bad value dmxLightbox for attribute rel on element a: The string dmxlightbox is not a registered keyword. …htbox_2.html" rel="dmxLightbox" rev="{width:960, preset:'thin', plugin:'url'}">

Syntax of list of link-type keywords:A whitespace-separated list of link types, with no duplicate keywords in the list. Each link type must be listed as allowed on <a> and <area> in the HTML specification, or must be listed as allowed on <a> and <area> on the Microformats wiki, or must be an absolute URL. You can register link types on the Microformats wiki yourself.

Website URL: mgclimate.com/

Is there anything I need to do?

Hello,
That is not really an issue and you should not be worried about it.
Checking your website i see many other issues that you should be worried about - like slow loading time, using images for the navigation background, using huge transparent png files, slow loading time on mobile due to animating every single element on your page, bad readability etc.. that will cause you lots problems than the rel warning.
Anyway - the rel will be improved in the upcoming update of dmxzone lightbox, so the validation won't warn you again.

Hi Teodor,
Has this been improved yet?