I find those two modules in Tridion driven application's web.config, I am not sure what is the purpose or whether I should comment it out. Anybody knows what they are for?
<add name="Tridion.ContentDelivery.AmbientData.HttpModule" type="Tridion.ContentDelivery.AmbientData.HttpModule" />
<add name="Tridion.ContentDelivery.Preview.Web.PreviewContentModule" type="Tridion.ContentDelivery.Preview.Web.PreviewContentModule" />