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">
Other tags that got simpler:
<input type="checkbox" checked="checked">
are now "naked"
<input type="checkbox" checked>
Other naked attributes:
Things Got Semantic
Instead of designing your web page structure with div tags like this
you can now use a "semantic" tag like this
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: