WebResource.axd provides access to embedded resources within a project. It's a handler that enables control and page developers to download resources that are embedded in an assembly to the end user. You include WebResources in your AssemblyInfo: [ assembly : System . Web . UI . WebResource ( "Project.Styles.Main.css" , "text/css" )] Then you can get an include path for your Page using the following code: string includeLocation = Page . ClientScript . GetWebResourceUrl ( this . GetType (), "Project.Styles.Main.css" ); Then to add the above file (which is a CSS file in this case): LiteralControl include = new LiteralControl ( String . Format ( includeTemplate , includeLocation )); (( System . Web . UI . HtmlControls . HtmlHead ) Page . Header ). Controls . Add ( include ); Then you'll end up seeing references within your page source such as the following: / WebResource . axd ? d = PhPk80h_UWEcbheb - ...