High Performance Web Sites

Home Pages

The only exception I've seen where inlining is preferable is with home pages. A home page is the URL chosen as the browser's default page, such as Yahoo! home page (http://www.yahoo.com) and My Yahoo! (http://my.yahoo.com). Let's look at the three metrics from the perspective of home pages:

Page views

Home pages have a high number of page views per month. By definition, whenever the browser is opened, the home page is visited. However, there is often only one page view per session.

Empty cache vs. primed cache

The primed cache percentage might be lower than other sites. For security reasons, many users elect to clear the cache every time they close the browser. The next time they open the browser it generates an empty cache page view of the home page.

Component reuse

The reuse rate is low. Many home pages are the only page a user visits on the site, so there is really no reuse.

Analyzing these metrics, there's an inclination toward inlining over using external files. Home pages have one more factor that tips the scale toward inlining: they have a high demand for responsiveness, even in the empty cache scenario. If a company decides to launch a campaign encouraging users to set their home pages to the company's site, the last thing they want is a slow home page. For the company's home page campaign to succeed, the page must be fast.

There's no single answer that applies to all home pages. The factors highlighted here must be evaluated for the home page in question. If inlining ...