Every Internet user's impressions of a website is greatly affected by how quickly that site's pages are presented to the user, relative to their expectations — regardless of whether they have a broadband or narrowband connection. Web developers often assume that most page-loading performance problems originate on the back-end, and thus the developers have little control over performance on the front-end, i.e., directly in the visitor's browser. But Steve Souders, head of site performance at Yahoo, argues otherwise in his book, High Performance Web Sites: Essential Knowledge for Frontend Engineers.
The typical Web developer — particularly one well-versed in database programming — might believe that the bulk of a Web page's response time is consumed in delivering the HTML document from the Web server, and in performing other back-end tasks, such as querying a database for the values presented in the page. But the author quantitatively demonstrates that — at least for what are arguably the top 10 sites — less than 20 percent of the total response time is consumed by downloading the HTML document. Consequently, more than 80 percent of the response time is spent on front-end processing — specifically, downloading all of the components other than the HTML document itself. In turn, cutting that front-end load in half would improve the total response time by more than 40 percent. At first glance, this may seem insignificant, given how few seconds or even deciseconds it takes for the typical Web page to appear using broadband. But any delays, even a fraction of a second, accumulate in reducing the satisfaction of the user. Likewise, improved site performance not only benefits the site visitor, in terms of faster page loading, but also the site owner, with reduced bandwidth costs and happier site visitors.
Creators and maintainers of websites of all sizes should thus take a strong interest in the advice provided by "Chief Performance Yahoo!", in the 14 rules for improving website performance that he has learned in the trenches. High Performance Web Sites was published on 11 September 2007, by O'Reilly Media, under the ISBN 978-0596529307. As with all of their other titles, the publisher provides a page for the book, where visitors can purchase or register a copy of the book, or read online versions of its table of contents, index, and a sample chapter, "Rule 4: Gzip Components" (Chapter 4), as a PDF file. In addition, visitors can read or contribute reviews of the book, as well as errata — of which there are none, as of this writing. O'Reilly's site also hosts a video titled "High Performance Web Sites: 14 Rules for Faster Pages", in which the author talks about his site performance best practices.
The bulk of the book's information is contained in 14 chapters, with each one corresponding to one of the performance rules. Preceding this material are two chapters on the importance of front-end performance, and an overview of HTTP. Together these form a well-chosen springboard for launching into the performance rules. In an additional and last chapter, "Deconstructing 10 Top Sites", the author analyzes the performance of 10 major websites, including his own, Yahoo, to provide real-world examples of how the implementation of his performance rules could make a dramatic difference in the response times of those sites. These test results and his analysis are preceded by a discussion of page weight, response times, YSlow grading, and details on how he performed the testing. Naturally, if and when a reader peruses those sites, checking their performance at the time, the owners of those sites may have fixed most if not all of the performance problems pointed out by Steve Souders. If they have not, then they have no excuse, if only because of the publication of this book.
The book is a quick read compared to most technical books, and not just due to its relatively small size (168 pages), but also the writing style. Admittedly, this may be partly the result of O'Reilly's in-house and perhaps outsource editors — oftentimes the unsung heroes of publishing enterprises. This book is also valuable in that it offers the candid perspective of a Web performance expert, who never loses sight of the importance of the end-user experience. (My favorite phrase in the book, on page 38, is: "...the HTML page is the progress indicator.")
In the book's final chapter, Steve Souders critiques the top 10 sites used as examples throughout the book, evaluating them for performance and specifically how they could improve that through the implementation of his 14 rules. In critiquing the website of his employer, he apparently pulls no punches — though few are needed, because the site ranks high in performance versus the others, as does Google. Such objectivity is appreciated.
For Web developers who would like to test the performance of the websites for which they are responsible, the author mentions in his final chapter the five primary tools that he used for evaluating the top 10 websites for the book, and, presumably, used for the work that he and his team do at Yahoo. These include YSlow, a tool that he created himself. Also, in Chapter 5, he briefly mentions another of his tools, sleep.cgi, a freely available Perl script that tests how delayed components affect Web pages.
Yet these weaknesses are inconsequential and easily fixable. The author's core ideas are clearly explained; the performance improvements are demonstrated; the book's production is excellent. High Performance Web Sites is highly recommended to all Web developers seriously interested in improving their site visitors' experiences.