The Semantic Web Project is a notion that all web pages on the Internet will become as readable by machines as they are by humans by unifying the way in which the information is presented. If the project achieves it's ultimate goal a web page containing text, images and other media just like the one you're reading now will serve solely as the structure holding the information and a selection of methods of presenting that information to different devices.
I think there are probably two general groups of readers that would ask this question and each requires a different response:
If you're new to the web and want to build a page there are several ways of going about this. Making a semantically harmonious XHTML web page is probably the easiest way to go about it. One of the first things you might want to do is make a web page about yourself. This tutorial will show you how to do that without needing to learn how to use any complicated software or buy a super computer.
Without going into pages of details XHTML web sites are easier to build and maintain. Designers can very quickly and easily change the look and feel of a website without having to alter every single page. Developers and coders can write scripts to produce "vanilla" XHTML making database design and server-side functionailty simpler and quicker to code and above all it allows you to place the content of your page in any order within the code so that search engines and spiders pick up on the page relevant content first not an image of a logo or a link to the homepage.
In a word... no. The look and feel of this website may not appeal to your tastes but you cannot argue it looks dull. Check the two W3C logos on the pages and you'll see that this site meets both the structural standards of XHTML and the style related standards of CSS. Its true that most websites you see bearing these standards marks aren't particularly visually rich but that isn't the fault of the standards, rather that designers regard standards as something coders try to achieve and on the whole coders view design as a something that pollutes clean efficient code. Those two ways of thinking are holding the Internet back.
So to recap semantically (meaningful) harmonious web pages area all things to all people and all machines and not only that they can be funky too. The wording of the explanation of the worked example assumes you can already make a new text file, rename it, open it in notepad text editor and so forth.
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