Can we run an asp.net application without a Web.config

If there is no Web.Config file, Application takes Machine.config settings as default settings

The root Web.config file inherits all of the settings in the Machine.config file. The root Web.config file includes settings that apply to all of the ASP.NET applications that run a specific version of the .NET Framework. Because each ASP.NET application inherits default configuration settings from the root Web.config file, you need to create Web.config files only for settings that override the default settings.