After learning that attribute names are case-sensitive, I found conflicting information.
A source mentioned that attribute names are indeed case-sensitive. For example, the width attributes in <div> and <DIV> would be considered separate due to their different cases;
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Curious about this, I conducted an experiment on JSFiddle:
HTML
<p ID="myId">Let's see if this is red</p>
CSS
#myId {color: red;}
To my surprise, the text did turn red as expected: http://jsfiddle.net/xtLr08u7/.
This made me question which information is correct.