FTA: "...browsers can render mockups that are just as beautiful as those created in an image editor"
This gets at something I never understood about the start-with-PSD school of web design: if it's not possible to get the effect you want in a browser, what is it doing in a mockup?
Yep. When I did a brief stint at an ad agency, we had print designers doing web layouts, which meant much of the design could not be rendered easily (or at all) via HTML and CSS. That meant we spent a fair bit of time cutting up PSDs and dumping the images into tables.
I wish, sadly they don't work in anything less than ie9, which isn't even out yet and will never be ported to xp. It will be a decade before it will be in general use, and by that time css3 will be as obsolete as ie6 is today.
Many "web designers" are great with Photoshop, but don't understand that a lot of special effects that are easy to make with Photoshop can be very time-consuming to pull off with HTML/CSS.
For the record, I think the ideal situation is to sketch out your design with pencil/paper and agree on a general layout before touching any code.
When dealing with clients though, unfortunately they may expect to see pixel-perfect photoshop mockups before agreeing that a design is what they want, which can complicate things.
the point is that you don't limit yourself from the outset by designing in code (i.e. you don't impose implementation restrictions that can be resolved with images/js/svg/whatever). it's a double edged sword, though, i don't think the article is exactly spot on here, you need to sort of bottom-up & top-down the whole process.
The reason you mock up in psd (gross) or fireworks or a sketch book (yay!) or anywhere is because you can be purely expressive in an orthogonal capacity than you would be if you were implementing in code from the start.
You ignore issues like "oh, will this p be in a div or in a series of lis contained by... blërg" while those implementation details are valid to keep in mind, they're not entirely crucial to address when you're sketching which is really the key word here.
This gets at something I never understood about the start-with-PSD school of web design: if it's not possible to get the effect you want in a browser, what is it doing in a mockup?