The front end engineer for a website holds in their hands a tremendous amount of power with regard to end users' experience of your site. They are the last line of defense and the decisions they make directly shape the experience that the user takes with them about your site, and ultimately, your product.

The goal of High Performance Web Sites is to make that experience a positive one, ;another goal is to change your approach to performance optimization. Steve Souders is the Chief Performance Yahoo!, where he specializes in making websites go faster.

High Performance Web Sites covers 146 pages in 15 chapters and two prependixes; these would be appendixes if they were at the back, but instead they come before the chapters.

Prependix A, "The Importance of Frontend Performance" describes the fact that 80 percent of the time of downloading a page is spent on the components on the page. Here is described tracking web performance and why focusing on the frontend is so important. Prependix B, "HTTP Overview" explains the parts of HTTP that are relevant to performance, as well as giving a short description of how HTTP works.

Chapter 1, "Make fewer HTTP Requests," shows that because every time the user requests a HTML document, they are requesting the components as well; one thing that can be done is to make fewer requests. Chapter 2, "Use a Content Delivery Network," explains that if you want to improve the time for the components to load, it is better to disperse the component web servers first.

Chapter 3, "Add an Expires Header," shows that by adding a future "expires" header, you can make those slow loading components cacheable. This will avoid unnecessary HTTP requests on subsequent page views. Chapter 4, "Gzip Components," explores the fact that by reducing the size of a page request, you can reduce the load time of the request. By using gzip encoding to compress the HTTP requests, you reduce the page weight, and hence, reduce the time factor.

Chapter 5, "Put Stylesheets at the Top," demonstrates that, because the page load is progressive; that is, what is delivered first is rendered first, you want the style sheet loaded at the top to allow the rest of the page to render as it loads. Chapter 6, "Put Scripts at the Bottom," shows that for the same reason of progressive rendering, you want to put the JavaScript at the bottom of the page so it executes after the page is rendered.