For me, Web 2.0 means that the page communicates with the server with something like AJAX or Websockets: content changes/is updated/is fetched from the server w

For me, Web 2.0 means that the page communicates with the server with something like AJAX or Websockets: content changes/is updated/is fetched from the server without a page reload; 1 web page = 1 HTTP request to an HTML page is not true. It's not related to a version of HTML or to CSS features.