I thought I have somehow [found a solution to the very vexing problem with Firefox and CDN-hosted fonts access](https://stackoverflow.com/questions/12229844/amazon-s3-cors-cross-origin-resource-sharing-and-firefox-cross-domain-font-loa), but here comes IE9.

I recently found a very frustrating issue with IE9 caching problem, and chanced upon this [blog post (IE9 Redirect Caching Nightmare)](http://blog.maskalik.com/asp-net/ie9-redirect-caching-nightmare) which enlightened me more about the actual issue.

I have to admit that I'm not sure whether the above mentioned is actually the issue, but it seems close enough.

**Problem:**

I have a website set up with 2 domains(base domain and subdomain) pointing to the same server, serving the exact same website which is using a same set of resources from a CDN hosted on Amazon S3, served by Cloudfront.

```
https://example.com
https://www.example.com

```

I get these kind of error messages in my IE9 developer tools console when loading fonts from my CSS file using @font-face:

```
CSS3117: @font-face failed cross-origin request. Resource access is restricted.

```

This happens when I loaded either of the URL first, then visiting the other second. IE9 is **not** running in `Compatibility Mode`. It running is in `Document Mode: IE9 Standards`.

From my limited understanding of the CORS and the need to set `Access-Control-Allow-Origin` HTTP header, I have dutifully set it up in S3 CORS policy, and it works perfectly fine with Firefox.

Requests from both domains, will get their respective header when requesting the CDN resource.

It seems that IE9 tried to do some optimization with caching, and cached the redirect too.
This causes a problem as the `Access-Control-Allow-Origin` header is cached as well. Without sending a request to the CDN server, the `Access-Control-Allow-Origin` header cannot change for different domains.

So I'm left with a situation where the request is from `https://www.example.com` and yet the `Access-Control-Allow-Origin` is `https://example.com`. This leads to the restricted resource problem with the error message above.

**Further look:** I did a check with Firefox 19, the above situation actually occurs, but it does not encounter the same strict restriction as IE9. Subdomain (`https://www.example.com`) requesting information will accept the `access-control-allow-origin` of the main domain(`https://example.com`). Chrome (Webkit) doesn't seem to care. I'm at a loss about which browser's behaviour implementation is correct.

With my current settings in the CDN, it seems like Chrome and Firefox, automatically reroutes all`www` subdomain requests to the main domain. Only upon multiple attempts of inputing the `www` subdomain in the address bar, then will Chrome and Firefox obey. IE9 on the other hand, just goes to whichever address is typed in the address bar. IE9 seems to be the odd one out here, but I'm not sure which browser's behaviour is actually correct.

From a usability standpoint, Chrome and Firefox seems to be the "correct" behaviour.

**Known Possible Solutions:**

1. Set `Access-Control-Allow-Origin` header to allow all, i.e. `*`
2. Turn off caching in the browser
3. Redirect one domain to the other
4. Use query string to differentiate different domain calls for resource
5. Embed the font into the CSS as data-uri

For solution 1, let's just say I'm paranoid that I just want to set specific domains to allow.

For solution 2, is not optimal if I were to set it for *all* browsers, also my site has to run on mobile devices with usually less-than-desirable download speeds.

For solution 3, possible, but I'm still curious for solution to deal directly with the IE9 caching issue.

For solution 4, it is very hard to implement especially when the resource is called from `@font-face`. Does it mean that I'll have to dynamically re-generate the CSS for different domain calls for the different line just to load a font to bypass the issue? Seems to defeat the purpose of CSS itself, and caching resources for that matter.

**edit:** Stylesheet works, font-loading doesn't.

For Solution 5, it is tedious for maintenance and updating, especially when there are changes to the font files periodically.

**Question:** Are there any known ways to deal specifically with IE9's redirect caching behaviour in this particular case?

Answers and comments are very much appreciated. Thanks in advance!

Edit: More browser test information.