I ran into the same problem with XML files exported from PowerShell that were built into iFrames.
There was no problem with IE10 / 11 or Edge, but Firefox and Chrome did not load the stylesheet.
The original iFrames page load was encoded in UTF8, the same with the style. However, the XML file was exported to UTF16LE (Unicode in PowerShell). When the XML file was loaded from iFrame, it loaded the stylesheet as Chinese characters.
I converted the encoding to PowerShell ...
Get-Content C:\foldername\file.html -Encoding Unicode | Set-Content -Encoding UTF8 C:\foldername\file.html
... and it worked! I assume that IE should treat the encoding of all files in the same way as the parent, which means that the encoded file UTF16LE was displayed as UTF8. Chrome and Firefox do not seem to do this.
Thanks to Xavier Holt for taking me on the right track!
Alarchy
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