High Performance Web Sites

Chapter 17. Deconstructing 10 Top Sites

What follows is an examination of 10 top U.S. web sites using the rules and tools described in this book. This analysis gives examples of how to identify performance improvements in real-world web sites. My hope is that after walking through these examples you will look at web sites with the critical eye of a performance advocate.

Page Weight, Response Time, YSlow Grade

Table 17-1 shows the page weight, response time, and YSlow grade for the home pages of 10 top U.S. web sites as measured in early 2007. YSlow is a performance tool developed at Yahoo! that produces a single score (A is best, F is worst) for how well a page satisfies the performance rules described in this book. See the upcoming section "How the Tests Were Done" for more information.

Table 17-1. Performance summary of 10 top U.S. web sites

Â	Page weight	Response time	YSlow grade
Amazon	405K	15.9 sec	D
AOL	182K	11.5 sec	F
CNN	502K	22.4 sec	F
eBay	275K	9.6 sec	C
Google	18K	1.7 sec	A
MSN	221K	9.3 sec	F
MySpace	205K	7.8 sec	D
Wikipedia	106K	6.2 sec	C
Yahoo!	178K	5.9 sec	A
YouTube	139K	9.6 sec	D

Not surprisingly, page weight and response time are strongly correlated, with a correlation coefficient of 0.94, as shown in Figure 17-1. This makes sense—adding more components or larger components to the page makes it slower. Plotting page weight and response time throughout the development process is a worthwhile analysis for any web page undergoing performance improvements.

Figure 17-1. Page weight and response time are correlated ...