html tag has 28px to margin which seems to come from nowhere

I'm getting this top margin from alexchen.info #2. I'm not sure what's that. It is not my 开发者_StackOverflowCSS file (style.css).

I'm not sure what other information provide. Any suggestions?

That's most likely the space taken up by the admin bar introduced in WordPress 3.1. I don't know why they'd put an admin bar on the frontend and not the admin page, but that's how it is.

Go to your admin profile page and you can turn it off from there (or enable it only on the admin panel).

See also http://wordpress.org/support/topic/margin-top-added-to-html-and-body-tags-after-upgrade-to-31

Try putting html{ margin-top: 0 !important; } in the last line of the last CSS document linked to..