404 Errors and 404 Pages

If a site has undiscovered missing images, JavaScript, or CSS files, it causes a 404 error for the page. You can use any link crawler to find broken links or missing images during non-peak times. You can also use Firebug to identify 404 error messages on a page. These might not be visible, due to a missing JavaScript or a missing include, but should be removed to improve performance. It impacts performance because the missing item can't be cached and therefore tries to retrieve it each time the request is made.

404 pages also impact the selling potential of a site. If a customer searches for an item that doesn't exist, they might receive a 404 error page. It's important to customize 404 pages, so that customers are drawn back to the shopping experience if they experience a 404 error, rather than clicking away. Salesforce recommends adding the following to 404 pages:

Related Links

Tools for Improving Site Performance

Techniques for Improving Site Performance

Testing Site Performance

Optimizing First Pages

Optimizing General Site Pages

Make Fewer Smaller HTTP Requests

Reduce and Reuse Scripts

Reduce URL and Page Size

Performance and Stability Coding Standards