Rule 3: Add an Expires Header(Chapter 3 of High performance Web Sites)
Fast response time is not your only consideration when designing web pages.If it
were, then we’d all take Rule 1 to an extreme and place no images, scripts, or
stylesheets in our pages.However, we all understand that images, scripts, and
stylesheets can enhance the user experience, even if it means that the page will take
longer to load.Rule 3, described in this chapter, shows how you can improve page
performance by making sure these components are configured to maximize the
browser’s caching capabilities.
Today’s web pages include many components and that number continues to grow.A
first-time visitor to your page may have to make several HTTP requests, but by using
a future Expires header, you make those components cacheable.This avoids unnecessary
HTTP requests on subsequent page views.A future Expires header is most
often used with images, but it should be used on all components, including scripts,
stylesheets, and Flash.Most top web sites are not currently doing this.In this chapter,
I point out these sites and show why their pages aren’t as fast as they could be.
Adding a future Expires header incurs some additional development costs, as
described in the section “Revving Filenames.”
Expires Header
Max-Age and mod_expires
were, then we’d all take Rule 1 to an extreme and place no images, scripts, or
stylesheets in our pages.However, we all understand that images, scripts, and
stylesheets can enhance the user experience, even if it means that the page will take
longer to load.Rule 3, described in this chapter, shows how you can improve page
performance by making sure these components are configured to maximize the
browser’s caching capabilities.
Today’s web pages include many components and that number continues to grow.A
first-time visitor to your page may have to make several HTTP requests, but by using
a future Expires header, you make those components cacheable.This avoids unnecessary
HTTP requests on subsequent page views.A future Expires header is most
often used with images, but it should be used on all components, including scripts,
stylesheets, and Flash.Most top web sites are not currently doing this.In this chapter,
I point out these sites and show why their pages aren’t as fast as they could be.
Adding a future Expires header incurs some additional development costs, as
described in the section “Revving Filenames.”
Expires Header
1 Expires: Thu, 15 Apr 2010 20:00:00 GMT
Max-Age and mod_expires
1 Cache-Control: max-age=315360000
