Does a responsive design loaded at 320px load the assets for the desktop version? Unfortunately it does.
Every background image specified in your CSS for higher resolutions is loaded (see comments); every element that you hid with
display: none; too.
Some think loading the site at 320px effectively prevents the CSS rules for 960px to execute. This is a common misconception about media queries usage. If your visitors are on a slow mobile connection, your site will load as slow as the desktop version does, even if it’s a responsive design.
City Crawlers Berlin kills that big image carousel at the top by using display:none, serving 1.8 MB of invisible images to mobile users. Crazy. A Different Design does the same thing with their content. This is easy to implement, but ultimately not a solution. Many other responsive sites display full res images to the desktop, only to squeeze them down on the client side when displayed on mobile.
The post that triggered writing this was Aaron’s post (quoted above) and some discussions I had at Fronteers. This is not a plea against responsive design — in fact, I’m all for it — but merely me trying to raise the general knowledge about when to choose for a separate mobile website and when a responsive design is sufficient.
If you’re interested in responsive webdesign, check out the presentation I gave saturday at Barcamp Ghent 4: back to the lab again (in Dutch).