I’m testing out my CSS at http://flexibletheme.tumblr.com/ and trying to make the website responsive to a small screen size.
Only problem is, I can’t get the padding to work on aside element. To reproduce the problem resize your browser window till the sidebar stops floating to the right (this will appear at the bottom, once the screen size is below width of 600px.
All the CSS is inline for now, to view the css. Part relevant to the resizing starts at:
@media screen and (max-width: 600px) {
Edit: This image shows the padding in purple (via Firebug) not displaying properly:

What about the padding isn’t working? Chrome’s web inspector seems to confirm that the padding is there as declared.
I do notice that your
<aside>element ends up positioned outside the left edge of your layout, but that’s because it’s floated right and haswidth: 100%;assigned to it.