Version 4 and prior of HTML was a little “wild west” in how it was interpreted and defined. It wasn’t always consistent in how it was implemented or interpreted, and sloppy interpreters allowed lots of pages with errors displayed things differently.
At one point it was estimated that 98% of all web pages had at least one error on it.
XHTML tried to formalize some processes, be more consistent in its rules, and be a bit stricter in following the rules. It encouraged an XML style of formatting with closing and self closing tags.
The developers behind HTML 5 made the specification less stringent and actually built flexibility into it.
Not only did they build new tags to handle images, audio and video, as well as organizational tags, but also added various JavaScript APIs (Application Programming Interface). A lot of the reason for focusing on new tags and APIs is because of where HTML5 started from, which was two different specifications: Web Forms 2.0 and Web Apps 1.0.
Additionally, HTML 5 incorporates CSS3 (Cascading Style Sheets version 3) to handle all of the styling. HTML 5 has tried to remove a lot of the styling from the HTML specification, just has XHTML tried to do.
The HTML 5 specification is considered to be a “living” specification, which means it is constantly under construction and changes to handle new features that users need based upon what browsers and technology can handle.
Intro to HTML 5 was originally found on Access 2 Learn
