This is a brief list of things I picked up while listening to the Stackoverflow Postcat #38:
1. Create a subdomain for serving images. Reason: A web browser usually only makes a maximum of two simultanious connections to a single domain. So if you move your images to a different domain, e.g. images.yourdomain.com, the browser makes more than two connections and downloads your site faster. As you see a subdomain is enough to do the trick.
2. Since web browser do very aggresiv caching of css files it happens that a web browser doesn’t pick up your updated css file until the user manually forces a refresh. A sulution is to add a version number to the name of your css file, e.g. style.css?3110. You can easily automate this task by using your current subversion revision number. This way you can force your client web browsers to use the latest css file.
3. Add a content-expires header to things like images to stop the web browser making even an request, to check if the ressource has changed. This minimizes the amount of http request needed to open your website.
There is a lot more to say to each of this points I guess, but it should serve as a reminder for me.