I would classify early web (1.0) as 1993-2003 (pre-AJAX), and modern web (2.0) as 2004-on (post-AJAX). The biggest change since then has been on the backend --

I would classify early web (1.0) as 1993-2003 (pre-AJAX), and modern web (2.0) as 2004-on (post-AJAX). The biggest change since then has been on the backend -- moving from web frameworks in Python/Ruby to Single Page Applications with Javascript backends.