Hacker News Reader

YSlow's primary purpose is to help you make sure the browser renders each page in the minimum amount of time. However YSlow does not only apply to browser rendering, following 6 of the 13 YSlow rules will result in a reduction of the total work the server must perform for each request.

I was under the impression it checked page retrieval times, which (after subtracting for idle network latency) would reveal which pages were transferring slow because of excess computation or disk use on the server. The idea being if it's slow for one user it's going to be _really_ slow for 1000+.

I've not more than installed and tried YSlow once, so I can't say too much about it.

It also looks at if you use a CDN, which may help him.