Don’t worry about responsive CSS performance. Let the browser optimize resource loading, it is already very good at it.
Don’t use Photoshop to create (slightly) rotated thumbnails; you’re much better off leaving this stuff to CSS.
There is no good solution for responsive images as of yet. Matt Wilcox goes through all currently proposed solutions and analyses them in depth. An excellent technical read.
Chris Coyier (I don’t think he needs an introduction) answers a couple of CSS related questions. Covered topics include box-sizing, CSS sprites workflow, CSS triangles, and server-side CSS optimization. Interesting and useful.
If you’re not (very) familiar with CSS Object Model, this is an article you should definitely read.
Are you tired of flipping back and forth between CSS and HTML files? Sure you are. Show markup in CSS comments and there will be no more flipping.
Some people are claiming that variables have no place in CSS. This must be sad time for them, because CSS variables have just recently landed in WebKit.
Until next week