Souders, who was speaking at Microsoft developer conference TechEd, said that while developers were aware of the need to improve performance, they were tackling the wrong things. They were cutting the number of requests to the web server; shrinking JPEG sizes or employing a content delivery network vendor like Akamai Technologies, all of which had minimal effect said Souders.
"We used to tear apart the Apache [web server] code to figure out what Yahoo was doing," said Souders, who was previously at Yahoo.
But after performing a detailed analysis, Souders discovered something startling: Only 10 percent to 20 percent of the time it took to load a website could be attributed to the web server.
That may have made sense a decade ago, but in today's era of PCs powered by dual and quad-core CPUs, it doesn't. And the cost of the delays created can be high.
Google has found that a 500-millisecond delay results in a 20 percent decrease in web traffic, while Amazon has seen a 100 millisecond delay cutting its sales by 1 percent, Souders said.
To fix, Souders first recommends a free tool he created called Yslow that analyses and then grades how well a web page is designed for maximum speed. Originally developed for Internet Explorer, Yslow 2.0 is an add-on for Firefox integrated with the Firebug web development tool.
Yslow analyses 22 criteria in all. It is unsparing in its ranking. Popular Web sites such as Apple.com, ESPN.com and Wikipedia, received a "C" from Yslow, while other popular sites earned an even worse "E."
"When I look at it, I feel like the teacher who hands out very severe grades," he said. Search engines with minimal content on the page, such as Google and Microsoft's Live.com, are among the rare sites that get an A from Yslow.
There are other tools besides Yslow for diagnosing performance bottlenecks. Microsoft offers the Visual Roundtrip Organizer, while AOL developed a now-open-source tool called PageTest.
All these tools judge website performance by a set of rules, though none of them matches YSlow's 22 criteria.
Souders' Powerpoint presentation is available online.
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