Netscape Navigator (more info on wikipedia). I've just searched for it and found out that it's been discontinued at its last version 22.214.171.124, on 1st March 2008.
HTML5 looks like a really advanced language that is still evolving, making it even more relevant to the needs of web content developers and web users alike, for the internet, today and tomorrow.
A lot of time was spent trying to figure out some peculiar conventions, and ways to do things. Looking up the documentation from www.w3schools.com's reference and tutorials. This is where I look up everything I need, at the moment.