Cache (.css, .js files) in asp.net using Web.config

    <system.webServer>
    <staticContent>
      <clientCache cacheControlMaxAge="365.00:00:00" cacheControlMode="UseMaxAge" />     
    </staticContent>
 </system.webServer>

Refer link:

http://www.iis.net/ConfigReference/system.webServer/staticContent/clientCache