Just when I thought I knew something about HTML, they bring out HTML 5. That's the upcoming major revision of the HyperText Markup Language (HTML), which is the main method of making content (like this page) on the World Wide Web.
HTML's development stopped at HTML 4.01 in 1999, but web content has evolved so much since then that current HTML specs are inadequate for today's requirements.
Already, the new mobile version of Gmail running on the iPhone now and the new mobile version of Google Maps that will be available makes use of new features only available in HTML 5.
How will it affect you if you're not someone who makes web pages using code? There are a number of differences from HTML 4 but you probably won't notice them because they will appear to you as something like a faster loading page and new options on web sites - but HTML is hiding behind all this. Just go up to the top of the browser you're using right now, select VIEW, and PAGE SOURCE and take a peek. Then, sit back and be glad that someone is watching out for all that code.