The request starts with the client and processed through IIS. In IIS, there are 2 utilities- INetInfo.exe and ASPNet_ISAPI.dll the InetInfo.exe checks for the syntax and semantics of the request and then the request goes to the ASPNet_ISAPI.dll which is the filter to filter the .aspx files. Here the URL request split in to 2 parts- virtual directory and webpage. Now worker process which is nothing but the application factory basically contains all the virtual directories and checks for the current virtual directory. If this is first request, then there will be no Virtual directory available. Now the worker process (W3wp.exe) creates a memory area called as App Domain to check for the current page. As App Domain is the Page Handler factory so it contains all the processes pages. If this is the new page then it will not find here. The request further move to the Http Pipeline where the actual execution of the page happened by using the ProcessRequest method and creates the events of the page. After creation of event and execution of all the event, the html page gets back to the user.