IE doesn't work with localhost + port

The WWW3 article Setting the HTTP charset parameter specifies :

Content-Type: text/html; charset=utf-8

This defines Content-Type as having a blank before charset.

I know that you have already found out that this is indeed the problem, so the source of the problem is some very unimaginative programming by Microsoft or by some middle-man proxy.

There is probably an issue in your settings for IE.

The easiest way to fix this would be to open Internet Options, go to the advanced tab, and click "Reset Internet Explorer Settings". Make sure you choose that and not "Reset Advanced Settings", as this one does not encompass ALL settings.

If this does not work, please also try navigating using 127.0.0.1 instead of localhost. This is not likely to resolve the issue, but could sometimes create an issue.

Edit: I wanted to add that this could be an issue with IE11. I know that we have been having a lot of compatibility issues with it. If you do not want to rollback to IE10 and try that, you could always Emulate from the registry:

Under

HKLM\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\

you will create a key called:

FEATURE_BROWSER_EMULATION

and inside it, create a DWORD value:

iexplorer.exe

with a value of one of the following:

 IE8 - 8000 (or 8001)
 IE9 - 9000 (or 9001)
 IE10 - 10000 (or 10001)

We have had the most success with 10001.