High Performance Web Sites

eBay

Figure 17-10. http://www.ebay.com

The YSlow grade for eBay (http://www.ebay.com) is very close to a B. With a little bit of work it would perform well. The main problems are with Rules 1, 3, 9, and 13.

Rule 1: Make Fewer HTTP Requests

The eBay page has 10 scripts and 3 stylesheets. A simple fix would be to use the combination technique described in Chapter 3. Four of the scripts are loaded close together at the top of the page, and three are at the bottom of the page. These should be combined into a top script and a footer script, reducing 10 scripts to 5. The three stylesheets are all loaded close together and should also be combined.

Rule 3: Add an Expires Header

One script and one stylesheet have an Expires header that is only nine hours in the future. According to the Last-Modified date, the stylesheet hasn't been modified in 3 days, and the script in 24 days. These are likely assets that change over time, but given the number of users of the site, it would be better to use a far future Expires header to make these files cacheable. Additionally, there are five IFrames without an Expires header. These are used to insert ad images, some of which don't have an Expires header as well.

Rule 9: Reduce DNS Lookups

Nine different domains are used in the eBay page. Typically, a domain count this high includes several domains from third-party advertisers, but in this case, there are seven ...