What's the proper way to add selected and related attributes to inputs?

Question

Asked by Unnamed At 08 October at 21:43

What is the proper way (standards compliant) way to add selected, disabled and similar attributes to <input> elements in HTML?

I have seen:

<input type="text" disabled>

<input type="text" disabled="disabled">

<input type="text" disabled="yes">

As far as I can tell, they all work, regardless of what the attribute's value is.
What is the right way to do this?

TechQA.