content-delivery-network

I have seen a number of questions that don't answer this, is it possible to check someones bandwidth using java script and load specific content based on it? The BBC seem to give me low quality images when using my mobile and in the middle of nowhere. by the looks of this this cool service does this and its a CDN so it could be server side. http://www.resrc.it/docs/ Does anyone know how they do it? or how I could do it using asp.net or javascript, or an community opensource plug in. I think it may be possible with https://github.com/yahoo/boomerang/ but not sure this is its true purpose.

When you look at a profile picture on a social networking site like Twitter, they store image files like: http://a1.twimg.com/profile_images/1082228637/a-smile_twitter_100.jpg or even with a date somewhere in the path like 20110912. The only immediate benefit I can think of is preventing a bot from going through and downloading all files in your storage in a linear fashion. Am I missing any other benefits? What is the best way to go about randomizing it? I am using Amazon S3 so I will have one subdomain serving all my static content. My plan was to store an integer ID in my database and then