Using $.append() to <link> a stylesheet fails in IE9.
#7350 identifies this bug, but it was closed as there was no test case given initially, and no response from the reporter when one was requested.
Here's a link to a test case:
This test case uses jQ 1.5, but I tested with 1.4.2, 1.4.3, and 1.4.4 with the same results.
This page loads 5 CSS stylesheets. Each stylesheet contains a single rule which applies to a different span.class, and each is loaded with a different method.
All the stylesheets load correctly with FireFox, Chrome and Safari, IE7 and IE8.
Using IE9-RC1 (9.0.8080.16413) stylesheets linked via $.append() are not loaded.
In the CSS tab of IE Developer Tools, the affected stylesheets report the error: "This stylesheet cannot be viewed because it's source is in a different domain than the page." Capturing requests from the Network tab shows that they are requested and served properly, but IE is just not using them.
Changing the document mode to IE7 or IE8 resolves the issue.
I can reduce this test case further if deemed necessary, but I found it useful to see examples of what does work alongside what doesn't.