Seperating the static content to a light-weight server?

Every time a request comes to a web server it goes though a stack of libraries to process the request. e.g. in IIS when a request to a .aspx comes it goes through the aspnet_isapi.dll to process the request. Simillerly if a request to a static content like .css files or image files comes, then also it has to go through the costly isapi processing. An alternative for this is to have static content served in a lightweight web server and have a url-rewriter in place at the main server (to redirect the requests to static content to the light weight server) which could result in a large performance gain.

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