The following comes from their newsletter and are some optimization tips they present get your site to render quickly:
Loadevent.Well, that's pretty much it. And if your server-side configuration is solid, it's going to be very difficult to be very, very slow. Unless, of course, you don't optimize images. A little trick we've recently discovered is that PageSpeed Chrome extension provides a little handy tool to optimize images aggressively. Once you install the extension and run it for a given website, you'll find a tab called "Optimize Images". It doesn't just show a list of unoptimized files but also allows you to open and save perfectly optimized files without using any external tools. The compression is usually at least as good as in popular compression tools.So that's basically the strategy we followed on Smashing Magazine, resulting inGoogle PageSpeed Score 97–99 — both on desktop and on mobile (although it varies depending on the advertising we display). Building a fast responsive site isn't that difficult as long as you are strict about what is and what isn't important on the page. For example, we defer loading of ads, tracking scripts, syntax highlighting, web fonts and other non-critical resources, all of which have helped us immensely speed up the entire site.Nevertheless, some work still lies ahead of us. We are planning to move to new servers soon (server response time is just unacceptable with our current provider), and will defer the loading of Gravatars on article pages as well as move to SPDY shortly. An article explaining all of the mini-optimizations we've done over the last few months will be published on SmashingMag in early September.Bottom line: if somebody tells you that responsive sites are fat, bloated, unusable and take too much time to develop, tell them that they're wrong. It's animplementation problem, not the technique itself. And with a proper strategy, it can be done right.— Stay responsive!