Internet Explorer Download Problem: “Unable to open this Internet Site”

Internet Explorer 7/8 throws an error when you pop a download through a meta refresh or iframe. The error message looks like this (I’ve blurred the domain as it’s not public yet):

Internet Explorer - Unable to open this Internet site

Searching around didn’t reveal anything of any particular use. Most “solutions” were for clients, which when you’re running a server, doesn’t help much.

Anyways, I decided to go back to basics, and try something really simple… Change the MIME type.

While the MIME type should be “application/octet-stream” for a binary setup file (program installer). However, simply changing it to “application/zip” fixes the problem in Internet Explorer, and popping meta refresh downloads then works.

In code (ASP.NET/C#):

// This does not work:
Response.ContentType = "application/octet-stream";
// This works:
Response.ContentType = "application/zip";

Now, I’m quite certain you could put in some other MIME type to get a popped download working, but it really doesn’t matter much whether it’s “zip” or “x-gzip” or “x-lick-me-internet-explorer”, just so long as it works.

In any event, the point is that Internet Explorer does not like “octet-stream” MIME types for popping downloads. This makes sense though as you kind of need to know a bit about what you’re doing to mess around with MIME types, and it limits the ability of spammers to distribute malware, or at least the low-level spammers that don’t really understand much more than what they read in spam forums.

I hope that helps someone avoid a bit of pain.

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2 thoughts on “Internet Explorer Download Problem: “Unable to open this Internet Site”

    1. IIS compression presents a few problems when files are already compressed, and shouldn’t be used for them (compressed files). I wrote a bit on the topic here:

      Broken Downloads in Internet Explorer from IIS Compression

      But, I already had compression enabled there, so I’m not quite sure what you meant there.

      The problem here is related to another issue in Firefox where FF renames files:

      Firefox renames files with a ZIP extension if MIME type is set to application/zip

      They say it’s a security issue, and that’s fine. It’s just not expected behaviour as file extensions are entirely arbitrary and by convention.

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