WordPress on IIS web.config with headers and cache control. Be sure to update "http://mydomain.com" with your site domain.

web.config

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <httpProtocol>
      <customHeaders>
        <remove name="Vary"></remove>
        <add name="Vary" value="Accept-Encoding"></add>
      </customHeaders>
    </httpProtocol>
    <staticContent>
      <clientCache cacheControlCustom="public" cacheControlMode="UseMaxAge" cacheControlMaxAge="365.00:00:00" />
    </staticContent>
    <rewrite>
      <rules>
        <rule name="WordPress: http://mydomain.com" patternSyntax="Wildcard">
          <match url="*"/>
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true"/>
            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true"/>
          </conditions>
          <action type="Rewrite" url="index.php"/>
	 </rule>
      </rules>
    </rewrite>
  </system.webServer>
</configuration>

web.config (WP Super Cache Support)

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <httpProtocol>
      <customHeaders>
        <remove name="Vary"></remove>
        <add name="Vary" value="Accept-Encoding"></add>
      </customHeaders>
    </httpProtocol>
    <staticContent>
      <clientCache cacheControlCustom="public" cacheControlMode="UseMaxAge" cacheControlMaxAge="365.00:00:00" />
    </staticContent>
    <rewrite>
      <rules>
        <!-- Begin WP Super Cache: http://www.am22tech.com/speed-up-wordpress-on-iis-windows-wp-super-cache/ -->
        <rule name="WP super cache Windows WordPress" stopProcessing="true">  
          <match url="(.*)" />  
          <conditions logicalGrouping="MatchAll">  
            <add input="{REQUEST_METHOD}" pattern="^POST$" negate="true" />  
            <add input="{QUERY_STRING}" pattern=".*=.*" negate="true" />  
            <add input="{QUERY_STRING}" pattern=".*attachment_id=.*" negate="true" />  
            <add input="{HTTP_COOKIE}" pattern="^.*(comment_author_|wordpress|wp-postpass_).*$" negate="true" />  
            <add input="{DOCUMENT_ROOT}/wp-content/cache/supercache/{HTTP_HOST}/{R:1}index.html" matchType="IsFile" />  
          </conditions>  
          <action type="Rewrite" url="wp-content/cache/supercache/{HTTP_HOST}/{R:1}index.html" />  
        </rule>
        <!-- End WP Super Cache -->
        <rule name="WordPress: http://mydomain.com" patternSyntax="Wildcard">
          <match url="*"/>
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true"/>
            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true"/>
          </conditions>
          <action type="Rewrite" url="index.php"/>
        </rule>
      </rules>
    </rewrite>
  </system.webServer>
</configuration>