>On active Web sites, such as this one and some I built for clients, the site is always responding immediately as there is always something hitting the server. But, on development server, on all those I have been working with so far, I see that IIS goes down if no more hit is arriving. So, basically, it takes longer to start again on the next hit, if no hit has been hitting the server for several minutes. HTTP Keep Alive is checked. But, I have the situation. So, I am trying to figure out where is that setting that will make IIS always respond fast even if no hit has been happening in the last hour?

I think you can control how long IIS waits to shut down an unused process by extending it in the App pool performance settings. Default is 20 mins? But it is probably a good idea to have the process re-start occasionally (in case of memory leaks etc). IIRC there's a setting somewhere which will force it to recycle if memory usage exceeds a certain level. The default behaviour then is to start up a new instance to accept requests *before* the old instance shuts down.

If you're using ASP.NET 4 you can configure this to run the app start code on startup (i.e. before a hit is received):
http://weblogs.asp.net/scottgu/archive/2009/09/15/auto-start-asp-net-applications-vs-2010-and-net-4-0-series.aspx

The question then is whether that process will complete *before* IIS starts passing requests to the new instance. I don't know the answer to that so only testing will tell :-{

Haven't we been here before ?

UPDATE: Just actually read the link I posted and that confirms that the warm-up *does* complete before any requests are redirected...