The lingo of the web, Hypertext Markup Language more commonly referred to as HTML, has grown in many ways since its creation. HTML has had to keep pace with the ever changing World Wide Web and as a result there are now several different versions of HTML.
In The Beginning
Hypertext Markup Language was originally created to share hypertext online documentation, news, mail, hypermedia, etc. The first version of HTML was the backbone of what we now call the World Wide Web. Can you imagine the web without images? The first HTML version was not able to display graphics as it did not support the image tag.
In the beginning there was no standardization either which meant that different browsers displayed web pages differently from each other. Even today you can see differences in web pages depending on which browser you use, but the slight differences you see today are minute compared to the first version of HTML.
As you can imagine the lack of standardization created many growing pains as the World Wide Web grew in size and acceptance. As a result HTML changed to keep up with the ever growing web. In an attempt to formalize HTML, version 2 was created and was the basis for web browsers. After several versions throughout the years, version 4.01 is the current standard, widely used today.
XHTML The successor to HTML
The next generation of HTML is XHTML which is just a stricter HTML version. This stricter version of HTML was introduced as more and more people are using laptops with wireless computing, mobile phones, PDA's, etc.
Since XHTML is strictly standardized, automated validators can be used to find coding errors, unlike HTML which is often hard to test. XHTML should improve browser compatibility and make web pages easier to maintain also.
However change can be a long process as many older browsers can only render XHTML as HTML, as opposed to popular browsers that deliver XHTML correctly. The World Wide Web Consortium currently recommends the use of XHMTL 1.0, XHMTL 1.1 and HTML 4.01.
Just as the world is ever changing and evolving you can be sure that the World Wide Web will follow suit. It's evident that the progression from the first version of HTML to the latest XHMTL is only a fraction of the change that web users and designers will witness in the future.