Even worse, the browsers could not handle standard html. HTML was based on SGML and it has all the nice SGML features. Something like <title/Hello World/ was v

Even worse, the browsers could not handle standard html. HTML was based on SGML and it has all the nice SGML features. Something like <title/Hello World/ was valid HTML afair. But then the browser never implemented it properly, so html5 just describes the behaviour of the browsers.