At my work, ‘m many times involved in performance tuning of the applications. May it be a batch application or UI app, the culprit is always considered as the Data Layer. Its not true always. I worked on one UI application, where we tuned the data layer to the best possible state, but no luck. Recently I came across YSlow. YSlow checks how the HTTP protocol is implemented. ‘m almost a year late on this, but as rightly said Better Late Than Never.

Check this out!!

http://developer.yahoo.net/blog/archives/2007/08/yslow-podcast-screencast.html