html - In the DOM are node ids case sensititve?

Question

Is this HTML valid? Or is the id 'a' the same as the id 'A'?

<div id="a">alpha</div>
<div id="A">Alpha</div>

Answer 1

Yes. It is case-sensitive. Attribute values are always case-sensitive. Different browsers seem to be doing different things though.

Handling document.getElementById is different across browsers:

1. Mozilla performs case-sensitive search.

2. Internet Explorer: IE 8 and later performs case-sensitive search, while IE 7 and earlier performs case-insensitive search.