Web Site Design: Optimizing Page Load Times

[mandy]

It is widely accepted that fast-loading pages improve the user experience. In recent years, many sites have started using AJAX techniques to reduce latency. Rather than round-trip through the server retrieving a completely new page with every click, often the browser can either alter the layout of the page instantly or fetch a small amount of HTML, XML, or javascript from the server and alter the existing page. In either case, this significantly decreases the amount of time between a user click and the browser finishing rendering the new content.

However, for many sites that reference dozens of external objects, the majority of the page load time is spent in separate HTTP requests for images, javascript, and stylesheets. AJAX probably could help, but speeding up or eliminating these separate HTTP requests might help more, yet there isn't a common body of knowledge about how to do so.

While working on optimizing page load times for a high-profile AJAX application, I had a chance to investigate how much I could reduce latency due to external objects. Specifically, I looked into how the HTTP client implementation in common browsers and characteristics of common Internet connections affect page load time for pages with many small objects....

full article: http://www.die.net/musings/page_load_time/