* The text in the right column is centered, rather than aligned, and is thus ragged on both sides, making it harder to read and sloppy-looking.
* The leading on "beginner class" yeesh.
* The body copy in the left column is set at the same size as the header text in the right column.
* The right column has indistinct headers with inadequate contrast.
* The right column mixes header signifiers, in some cases using all uppercase, in others bold.
* The body copy in the left column uses an oblique sans and the right column uses a similar sans, minimizing contract (notice how the "after" design uses a true italic)
* The "sections" in the right column are set off with pointless thin rules, which is a design annoyance so basic that Tufte yells about it early in (iirc) The Visual Display Of Quantitative Information.
* The right column has no hierarchy, so the contact information is set in exactly the same prominence as the rest of the information, so clumsily that the URL runs into the margin.
I guess I could go on.
This is pretty basic "Non-Designers Design" Robin Williams stuff. I don't see how you can criticize this blog post by suggesting that the "before" design is better. It's not. It's artificially bad: someone took a reasonable design and a list of everything you can do wrong in a page design and built a demo.
I agree with another comment on this thread though about the clip-art; it muddled the point the article was trying to make. They should have worked the same clip art into the "before" picture if they wanted to do that.