WebForms Page Templates
To make a WebForm work properly on a Page, you must modify the Page Template of that Page to handle the WebForm. WebForms ships with a sample Page Template called MultipleWebForms Page Template, which is located in the folder Building Blocks\Tridion WebForms\General\ of your WebForms-enabled Publication. This is configured as a JSP Template, but you can use the same code for ASP.NET; all you need to do is set File Extension to aspx.
To create your own Page Template that you can add Forms to, use this Page Template as a basis. This Template includes the Template Building Block called MultipleWebForms Template Building Block, which contains the core functionality. But the Page Template also contains code to render the correct WebForms tags on the published Web page.