What's New in HTML5?

The Good News

HTML5 is just the HTML you already know and love (or not), with a bunch of new stuff! It's an evolution -- not a revolution -- so you don't have to learn a new way of thinking; just start using the new stuff.

Things Got Simpler

The old complex doctype tag
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
is now
<!DOCTYPE html>
Other tags that got simpler:
<html>,
<meta>,
<link>.

Attributes
<input type="checkbox" checked="checked">
are now "naked"
<input type="checkbox" checked>
Other naked attributes:
<disabled>,
<selected>.

Things Got Semantic

Instead of designing your web page structure with div tags like this
<div class="header">
you can now use a "semantic" tag like this
<header>
It doesn't change the way the page appears, so why would you use it? Think about how useful it might be to a screen reader or web crawler that's trying to make some sense out of your web page. The name of a class is not helpful to such programs, but a tag that's guaranteed to have an agreed-upon semantic meaning is.
Other semantic tags:
<footer>,
<nav>,
<article>,
<section>,
<aside>.