Why HTML should become a dead language
Go ahead, take a gander around the Internet. Lets see who is using HTML, and who is using XHTML.
- XHTML
- Blogger [Served as HTML]
- Opera [Served as XML]
- FireFox (Mozilla) [Served as HTML]
- Facebook [Served as HTML]
- MySpace [Served as HTML]
- Twitter [Served as HTML]
- W3C [Served as HTML]
- HTML
- Microsoft
- Yahoo!
- Apple
- WHATWG
As you can see, the "newer" websites are serving in XHTML. A few of them Transitional (mainly websites where users can input HTML), however, a large number of them are marked as XHTML 1.0 Strict using the W3C DTD.
On to my main point, HTML should NOT receive an update. The primary reason people want it to, is because it is FAMILIAR to designers and developers. However, HTML is very lax on how it is interpreted, a little too lax in my personal opinion.
An Example. <input type="text" disabled>. The tag does not end. Its interpreted as a single tag, and disabled means that its disabled. I, myself, find this to be horrible, horrible code. In XHTML, all tags must end, and all properties must have a value. Which is easier to program, an HTML or an XHTML parser?
Probably the XHTML. HTML was not designed to be parsed, and is really quite a pain to attempt to parse using such things like Regex, considering how lax of a language it is.
In my own personal opinion, HTML should become a dead language. Some people hold on to it, let them. Let them continue making their websites in Archaic HTML 4. But do we really need to run an update to it? No. We should, move to XHTML. XML has already proven to be a very dependable language. Its used in such popular applications like Jabber, and Twitter, and is used commonly with AJAX, which is the height of the "Web 2.0" Revolution.
So why are we trying to revise it? Why can't we adopt a stricter set of rules so that they can better be implemented? In my personal opinion, work on HTML should be halted, and moved to XHTML. I still believe that the W3C and WHATWG should work together on a new version of XHTML. XMLEvents and XForms should adopt the magnificent features that Web Forms 2.0 has created. Again, this is my personal opinion.
EDIT: Added What Some sites are served as. Its actually pretty depressing.
The Purpose of CSS in the Semantic Web
The Term Web x.x is overused like the bottom of a shoe, and because of such a term, its scoffed at, laughed at, and generally made fun of on any tech site or twitter you can find. However, the term does have some importance attached to it.
"Web 2.0" would best be defined as the Internet for Design. Web 2.0 cares more about the Design side of pages. The Fancy fonts used, the rounded borders, the interactivity (AJAX!). That is definitely what Web 2.0 is all about.
"Web 3.0" is all about Semantics. The important part is that the code can be extracted via a machine or script or something. Here, standards take importance. XML, Microformats; we have to have standards that dictate how to write our code so that a program like Operator can pull the relevant information from it.
Now, once we have a code like that, CSS becomes VERY important. We need to use CSS to position our elements and colour them to make them look useful to the viewer, not just the machine, while still having machine readable code.
You see what I'm getting at? If you still don't understand, try opening a random XML or RSS file (without a CSS, XSL, or XSLT file) in Opera. That's actually perfect rendering of an XML file, and that's what it would be to any ordinary user.
Thankfully, Microformats were designed with Human Readability in mind, so they will properly work (bare minimum) with the HTML that is used with them, but, obviously, CSS is important to make it look like something nice.
So, now you know, the importance of CSS in the Semantic Web. 
Important Links: