New HTML5 details tag

Found out about a new HTML5 tag called details that seems pretty interesting. Before it would take javascript to achieve this effect. I think it's also possible with CSS. It basically add an arrow that hides content and when the arrow is clicked it shows the content. Click it again and it hides the content.

Here's the link to the article

*So I tried an example in this post, which I've since changed. The result was interesting. It worked (don't think this site uses the html5 doctype) but it didn't work correctly. It scooped up the previous post and put that in the hidden content. Very strange