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Tuesday, August 22, 2006

Web Performance Engineering [3]

Continuing my series on Web performance guidelines, today I am reviewing another book -- Speed Up Your Site, by Andrew B. King, published by New Riders in 2003.

A while back, when I was reviewing Web Usability Books, I promised to cover Speed Up Your Site, but never got around to doing so -- for reasons I will explain. A full table of contents listing all 19 chapters is available online; in summary, the book has six parts:
Part I - The Psychology of Performance (38 pages)
Part II - Optimizing Markup: HTML and XHTML (99 pages)
Part III - DHTML Optimization: CSS and JavaScript (111 pages)
Part IV - Graphics and Multimedia Optimization (85 pages)
Part V - Search Engine Optimization (39 pages)
Part VI - Advanced Optimization Techniques (79 pages)
Part of my difficulty in reviewing this book was that I have mixed feelings about it. Naturally, I am always pleased to see an entire book devoted to performance issues. Also, Part I is particularly good. Containing 77 references, it is a very well-researched survey of an important subject rarely covered in books about Usability. On the other hand, I am not nearly as impressed with the rest of its advice and guidelines, for two reasons: their correctness, and their completeness.

First correctness. Regarding the actual content, my issue is not that Speed Up Your Site contains factual errors. As far as I can tell, its content is accurate. But some of its recommendations -- although they may indeed improve performance -- are so unnatural that they are not really the correct way to tackle the problem. This concern is summarized by Alexander Bunkenburg in this review on
This book concentrates almost exclusively on sending fewer bytes from the server to the browser. It gives a large collection of tricks how to write shorter html, xhtml, css, and JavaScript. Some of these tricks are useful. Others however go against standards, and some seriously go against maintainability. I'd be reluctant to give this book to my team. One may be tempted into shaving off bytes, spending a big effort and yet producing unmaintainable code.
The problems that can result from deliberately violating standards are highlighted by David Rose in another Amazon review:
In today's world, where "standards based" coding is becoming more prevalent and adherence to the W3C standards for HTML coding is being recommended, this book just grated on me. While there is a great deal of great information, there are also a large number of "gotchas" to watch out for as well.

The book proposes to use HTML tags without their corresponding closing tags, not to use required elements whenever possible, avoid using quotes in HTML tags, and many other ways of creating "non-valid" code. This will "optimize" your code a bit more by reducing the characters in it, but it will also create problems for you in the future.

In summary, while the book does give a lot of good information, it often steers you away from standard code. If you are unsure what is considered "standard" and required for creating valid XHTML/CSS, you are best served skipping this book as it will teach you to create invalid code.
Bunkenburg's review also touches on my second area of concern -- completeness. Any book about speeding up Web site performance should (in my view) at least mention all the important topics, to let the reader know what options exist. Some important topics that receive little or no coverage in Speed Up Your Site are:
  • Page Types: All pages are not created equal, and users' tolerance for delays changes depending on where they are in their interaction with a site. So a single page design approach cannot be applied to all pages.
  • Maximize content reuse: A common mistake as sites grow is to use many different names (URLs) for the same thing, reducing the efficiency of browser caching.
  • Ratio of HTML base to content: There is a significant difference between the way browsers handle the base (or index) portion of the page, and referenced content elements, which can affect page download time.
  • Image resizing: For efficient page rendering, it helps to specify HTML HEIGHT and WIDTH tags for all embedded images. And for download speed, avoid resizing images in the browser.
  • Performance of SSL: All online business sites use encryption, and pages that use SSL encryption incur significant overheads. This is an issue that demands a separate section in any book about site performance.
  • Content Delivery Networks (CDNs): Akamai went public in 1999, and was widely used by 2002. Mirror Image, Cable and Wireless (formerly Digital Island), and Speedera also offered CDN services in 2002. How can any book about speeding up your site not even mention this technology?
In fairness to King, any discussion of the book's coverage should point out the following disclaimer, which appears in its Introduction:
Although the primary emphasis is on optimizing client-side technologies, this book also covers server-side techniques and compression to squeeze the maximum performance out of your site. These are all techniques that most designers and authors can control. Instead of focusing on esoteric server-side tuning limited to system administrators, this book focuses on optimizing the content that you deliver. For a server-oriented look at performance, see Web Performance Tuning, by Patrick Killelea.
But most of the omissions I listed are not related to server-side tuning, and of the two that are (SSL and CDNs), only SSL is discussed by Patrick Killelea, and his only recommendation is to use an SSL accelerator card. And in 2002, CDN technology could hardly be considered "esoteric", especially in a book which, to quote its author, is "not for beginners".

There is a lot more to be said on most the above topics, and in future posts I will expand upon them.

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