Browser Cache Settings

Most Web browsers have adjustable settings that specify how Web pages should be updated. (At any time, however, a user can manually update a Web page, typically by clicking on a button named Refresh or Reload.) For example, Internet Explorer provides several options for specifying when the browser will go back to the originating page to check for a newer version than the one stored in the browser cache. These options, which are shown in Figure 6.4, include:
• Every visit to the page—Every time you visit a page, the browser checks to see if the page has changed since the last visit. If the page has changed, the browser displays the new page and stores a copy in the cache. This option increases the time it takes for Web pages to appear between pages you have already viewed.
• Every time you start Internet Explorer—The browser checks to see if the page has changed only when the page was viewed in an earlier session. Otherwise, all visits to the same page, in the same work session, pull data from the browser cache. This option increases performance for pages you have already viewed in a single session.
• Automatically—The browser checks to see if the page has changed only when the page was viewed in an earlier session. The browser also determines if images on the page are changing infrequently over time and check for newer images even less frequently. This option provides the best performance for pages you have already viewed.
• Never—The browser pulls all previously viewed pages from the cache and never checks to see whether pages have changed. This option increases performance for pages you have already viewed. To see the most current version of a page when using this option, you will be required to refresh the page.

Most browsers also provide an option to quickly clear the cache. Deleting the cache slows performance upon each initial visit to a Web page but provides the advantage of restoring disk space that was being used to store the cached pages.