A CDN is a collection of web servers distributed across multiple locations to deliver content more efficiently to users. The server selected for delivering content to a specific user is the one with the fewest network hops. [Yahoo]
Amazon S3 is among the most cost-effective CDN for hosting WordPress files but if you are not on S3 yet, you may well consider using the Dropbox service as a CDN to serve the static files of your WordPress blog.
How? There’s a new WordPress plugin in town that can help you effortlessly deploy all the static files associated with your WordPress theme to Dropbox.
It works something like this. You create a sub-folder in your Dropbox Public folder and replicate your WordPress theme folder structure here. Next grab the URL of this public folder, pass it to the Dropbox CDN plugin and it takes care* of everything else.
Will this really help improve performance? Based on the suggestion of David Bradley, I conducted a quick test to compare the loading speed from Amazon S3, Dropbox, Google CDN and my existing host which is Dreamhost.
An uncompressed JS file was served from all the four servers and the load time of Dropbox turned out to be among the lowest (see the blue bar) partly because Dropbox automatically served the file with gzip compression.
[*] The Dropbox CDN plugin will not work with WordPress themes where the file paths are hard-coded into the code. Check your header.php file to ensure that you use standard functions like bloginfo(‘stylesheet_directory’), etc. to echo the static file names.