This page tests out several “special” tags. View the source to check them out! For example, there's a “meta” tag that specifies the charset and an associated RSS feed via a “link” tag.
This link will search Google for “hello”! The URL is relative, but the “base” points it to a different origin, and causes it to open in a new tab.
This page will refresh every 3 seconds (thanks to a “meta” tag) and displays an alert when it loads (via a “script” tag). A “style” makes this text orange!