HTML5 and CSS3 introduces some new file types that enables us to create even better websites. We are now able to embed video, audio and custom fonts natively to any web page. Some of these file types are relatively new and not supported by the IIS web server by default. It’s file types like .m4v, .webm and .woff.

When a request is made to the IIS for these unsupported file types, we are met with the following error message:

HTTP Error 404.3 - Not Found

The page you are requesting cannot be served because of the extension configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map.

The problem is that the IIS doesn’t know how to serve these new files unless we tell it how. This can be easily done in the web.config’s <system.webServer> section by adding the following snippet:

<staticContent>
    <mimeMap fileExtension=".mp4" mimeType="video/mp4" />
    <mimeMap fileExtension=".m4v" mimeType="video/m4v" />
    <mimeMap fileExtension=".ogg" mimeType="video/ogg" />
    <mimeMap fileExtension=".ogv" mimeType="video/ogg" />
    <mimeMap fileExtension=".webm" mimeType="video/webm" />

    <mimeMap fileExtension=".oga" mimeType="audio/ogg" />
    <mimeMap fileExtension=".spx" mimeType="audio/ogg" />

    <mimeMap fileExtension=".svg" mimeType="image/svg+xml" />
    <mimeMap fileExtension=".svgz" mimeType="image/svg+xml" />

    <remove fileExtension=".eot" />
    <mimeMap fileExtension=".eot" mimeType="application/vnd.ms-fontobject" />
    <mimeMap fileExtension=".otf" mimeType="font/otf" />
    <mimeMap fileExtension=".woff" mimeType="font/x-woff" />
</staticContent>

The above snippet includes support for most video, audio and font file types used by HTML5 and CSS3.

Last time we took a look at the performance impact of using tabs vs. spaces in HTML files. One question that arose was whether or not it’s worthwhile to minify HTML when also using GZip. Let’s run the experiment.

I’ve collected a few real-world HTML files and done some minification and GZipping on them. Here’s the result:

Website	File size	Minified	Gzip	GZip & minified	Savings
amazon.com	218,642	197,032	53,793	49,008	9%
cnn.com	130,014	121,534	27,114	25,392	6%
twitter.com	53,465	46,608	12,262	11,416	7%
xbox.com	38,888	24,139	8,075	6,795	16%

These pages already do minification on various sections, but none of them minifies the whole document. If none of them used any minification, the savings would have been higher than the table shows.

So, according to the results, minification will provide an additional 6-16% lower file size with GZip enabled.

16% is a rather large saving on top of regular GZip, so the data suggests that we must use both GZip AND minification.

Remember, this is a rather small experiment with only 4 real-world websites. It would be interesting to expand the experiment for more accurate statistics.

For HTML minification in ASP.NET, I like to use WebMarkupMin or Meleze.Web.