Can’t validate – Bad value for attribute rel

Hi Cais,
Today I tried to validate my site, but I got a whole bunch of errors, caused by the fancybox: https://validator.w3.org/nu/?doc=https%3A%2F%2Fwww.tina-turner.nl%2Fblog%2F

It says “Bad value 2e4f135215ff67ba0e9936938829ed4c for attribute rel on element a: The string 2e4f135215ff67ba0e9936938829ed4c is not a registered keyword”.

I read something about it. Shouldn’t the rel attribute be replaced by “data-rel”? (https://stackoverflow.com/questions/16133223/validation-bad-value-first-for-attribute-rel-on-element-link)

Johanna