[benatkin]

"strictly speaking" is right. It's invalid but all major browsers will handle the code just fine. Browsers are pretty damn forgiving.

It's also an easy mistake to make. All someone has to do is create an element with an ID in a child template without checking to see if that ID is already used in a parent template.

[josephagoss]

Is it possible to enable some switch in Chrome to force the browser to render only correct code in dev mode? This would catch me making mistakes that otherwise go unnoticed.

On the note of forgiving browsers, I love how they are a very accepting interpreter of information, much like a human listening to someone's broken English and still understanding what is being said.