Reading material on the web, especially in today's rapid-speed society, can be categorized into two types: "chunking" and "scrolling", according to Writing for the Web, Chapter 2. Neither is better than the other; they serve different purposes.
Small chunks of around 100 words let the reader quickly digest the material and choose whether to continue navigating the website or move on. Large sections of text that readers have to scroll through are cumbersome, but the only way to display a full linear text like a writing sample or important document.
While I understand what Kilian is getting at, I only partially agree. Most of the websites I visit have large bouts of text, and most of my blog posts (and the blogs I follow and enjoy) are longer than 100-200 words. While most people browsing are of the "hit and run" category, there is still a whole section of cerebral people using the web who enjoy actually reading things and finding content of merit.
Kilian also talked about two other very important things for new web content writers to understand: subtext and the "vampire video" effect. You wouldn't go to a dentist with bad teeth anymore than you'd hire a freelance writer who obviously didn't bother to spell check his website. It's the same thing I always used to get in trouble for when I was younger: It's not what you said that was wrong, it was how you said it.
The "vampire video" effect stems back to when TV was a fairly new medium, and advertisers sunk all their funds into slick graphics that distracted people so much they missed the product. This was rampant on the web in the 90's, when every page you went to had crazy fonts, frames, animated gifs of Odie and smiley faces, custom cursors, welcome pop-ups, and 20 other things they didn't need but thought were cool. The website class I took in middle school used the Bells & Whistles site frequently for resources; they've evolved from a clipart and web graphics site to now having scripts and actual web development tools. When Internet speeds increased, people started adding videos, songs, and flash to their websites. Newcomers to websites often overload them with so much extra flashy stuff that you can't see the content for all the eye candy.
When developing a website, profile, or blog, a little goes a long way. Pick your best graphics and let them shine. Have a second set of eyes help you prune down your text for clarity and conciseness. Don't overwhelm your reader with too much stuff on the screen at once (break it into separate pages, for example), and avoid putting too-loud graphics or other distractions next to important content. Large blocks of text are okay, as long as you identify them and remember your audience - long blocks of text about the Jersey Shore will get you nowhere.