IIS 7.5 and images not being cached

Question

I cannot get the image files to cache. I have tried everything that I have found on this site and others and still cannot get them to cache.

Web config setting that

Answer 1

The following should cause the browsers to cache your images:

<staticContent>
    <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="1.00:00:00" />
</staticContent>
<httpProtocol>
    <customHeaders>
        <add name="Cache-Control" value="public" />
    </customHeaders>
</httpProtocol>

The <caching>...</caching> block is for server-side caching, not client side caching.

Answer 2

In case anyone needs to configure your site as Chrome Audits or GTMetrix require I've configured my environments with the following (thanks to Marco's answer):

<clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="365.00:00:00" />

using 365 days and both tools took that value as acceptable for a cache time.