A Syntax Question: Validating Meta Keys with Capital letters?

Dear folks, somewhere on the net I read a person advising:

" Validate your meta keys dude. Validating it would help (Mostly, make all letters CAPITAL and add / before the ending 开发者_如何学Go> "

What does that mean? does that mean

<link rel="canonical" href="<?=$canonical?>">

should be

<LINK REL="CANONICAL" HREF="<?=$canonical?>"/>

?? Thanks for clarification

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I think he talked only about attribute names.. ie.

<LINK REL="canonical" HREF="<?=$canonical?>" />

But case doesn't matter afaik. Ad. validation: He was probably talking about w3c html validator.