How do i set expiration on CSS, JS and Images for windows server (need use .htaccess or web.config)

Question

I get below error when i run google page speed tool Leverage browser caching Setting an expiry date or a maximum age in the HTTP headers for static resources instructs the browser to load previously downloaded resources from local disk rather than over the network. Leverage browser caching for the following cacheable resources:

http://www.clearskin.in/additional-css/medic/style.css (expiration not specified)