Web Performance Matters

Managing Response Time for Web Sites and Web Applications

Human beings don’t like to wait. We don’t like waiting in line at a store, we don’t like waiting for our food at a restaurant, and we definitely don’t like waiting for Web pages to load.

Those words open Web Page Response Time 101, an excellent article by Alberto Savoia. Although it was published in July 2001, it remains every bit as relevant and useful today.

Published by STQE, the magazine of software testing and quality engineering (now renamed as Better Software Magazine), this article does a really good job of explaining and summarizing two fundamental aspects of Web performance -- human behavior and site behavior.

Human behavior

First Alberto presents The Top Four Laws of Web Site Performance. Two of these four "laws" summarize the underlying human behaviors that make the response times of Web pages or Web applications so critical. These cover some of the same ground as my recent post highlighting Scott Barber's views on Acceptable Response Times:

The Law of Stickiness

Web site users are sticky, but they are not loyal.

That means that if they find a Web site that adequately serves their needs they tend to stick with it, but the moment that site disappoints them (by being slower than usual, or temporarily unavailable), they will move to a competitive site and stick with it…until that new site gives them reason to switch again. The implication of this law is obvious: do whatever you can to improve and maintain top performance, or users will abandon your Web site and start sticking around a competitor’s site.

The Law of Expectations

Users’ satisfaction with Web site performance is dictated by their expectations, and that their expectations are created by their previous experiences with other Web sites.

Let’s assume a user is accustomed to home pages that load in, say, six seconds. Given that expectation, if your Web site’s home page loads in ten seconds, that user will consider it slow, be dissatisfied, and will—probably—go somewhere else. The implication of this law is that whenever you measure Web site performance, you shouldn’t analyze the results against some absolute value; instead, analyze them relative to the performance numbers of other Web sites (especially your competitors’).

--Alberto Savoia, Web Page Response Time 101, STQE, July 2001.

Alberto's two other "laws" deal with the consequences of these human behaviors, for any organization that needs to manage the performance of its Web site or applications, to ensure acceptable levels of customer service:

The Law of User Perspective

You should measure your Web site’s performance from the end-user point of view.

When you pull up your Web site and test it from your intranet (running at 100Mbits/sec), performance might be fantastic—but most of your users will have to experience it through much smaller bandwidth. Under those conditions, that home page animation that looked so cool on your intranet will take forty seconds to load, and impatient users will not think it’s very cool at all.

The Law of Responsibility (a.k.a. It’s Always Your Fault)

Users don’t really care who’s responsible for a Web site’s poor response.

If they experience poor performance on your Web site, you’re the one who’s going to get the blame— even though the root of the performance problem may be a temporary glitch with their Internet Service Provider (ISP), or even with the Internet as a whole. The implication of this law is that you must be aware of all the factors that can impact your performance and take steps to eliminate or reduce them even if they seem to be out of your hands.

--Alberto Savoia, Web Page Response Time 101, STQE, July 2001.

Web site behavior

The remainder of the paper presents and explains a simple formula for Web page download time that I mentioned previously in my post on Yahoo! and Web Page Performance. I will discuss the formula and some related links in my next post.

If you'd like a reprint of Alberto's paper that's a bit easier to read than the online version I linked above, you can download a pdf version from the Performance Management section of my Papers and Talks page. [Warning: even though it's just 6 pages, it's a 2.5Mb file, so wait until you're on a fast connection].

Tags: Alberto Savoia, performance, performance objectives, response time, download time, Performance Matters, Web performance