Internet Explorer 9 Permanently Caches Redirects
Problem
Internet Explorer 9 (IE9) permanently caches redirects even if they are changed on the server. Symptoms include being "stuck" in the mobile view of a College of Ag Sciences site, or going to an old destination for a short URL. Clicking the "Non-mobile view" link at the bottom of the mobile site does not take you to the non-mobile view.
Solution
There appears to be no way to purge the redirect from the browser cache by using the standard cache purging functionality in the Internet Options configuration screen.
One method that appears to work:
- Clear your browser history and cache. These instructions are for IE8, but will work in IE9 as well.
- Go to the Tools menu and enable InPrivate Browsing (anonymous browsing) mode. This will open a new window
- Paste the original URL of the page that incorrectly redirects into the URL bar of the new window
- If you are experiencing trouble with an AgSci mobile site, click the "Non-mobile view" link at the bottom of the page while within the InPrivate mode.
- Close and restart Internet Explorer
Technical Information
According to a post in the Microsoft Answers forum, this functionality is new in IE9 and makes 301 (Permanent) redirects absolutely permanent. However, search engines require 301 redirects rather than 302 (Temporary) redirects in order to adjust their indexes.
In general, the AgSci sites use 301 redirects to prevent broken links when moving content. After observing and diagnosing this problem, we changed the AgSci mobile sites to use 302 redirects when redirecting mobile users to the mobile site. However, anyone still "stuck" in the mobile site should use the workaround above.
More information
- Caching Improvements in Internet Explorer 9 - "Redirect Caching" section
- Microsoft Answers Forum: (possible) bug in IE with HTTP code 301 - Permanent Redirect
