I have a question about this new:

<meta charset="UTF-8">

thing, introduced in HTML 5. Why it's not self-closing tag? I don't understand it, I think it should be:

<meta charset="UTF-8" />

Can anyone explain it to me?

That's not new, its standard practice for XHTML and has been for years. HTML5 picks up with the same conventions as XHTML - ALL tags MUST be closed.

You might want to read this recent article:
http://www.alistapart.com/articles/g...dy-for-html-5/

It is standard practice of XHTML that all the open tag should be closed