Error about runat=server!!

Question

I inserted all my HTML pages into ASP.NET and edited the code for ASP to run. But i keep getting an error about runat=server. The error is about my LinkButtons, Buttons and Textboxes who supposively aren't in runat=server or whatever that's for. This is the error i get on almost every page. Only my registration form and Login form i don't get this error but I did that e few days before. Control 'txtGebruiker' of type 'TextBox' must be placed inside a form tag with runat=server. I changed my HTML code when inserting it into ASP.NET: so i deleted the ordinary textboxes and made new ones by means of the Toolbox in Visual Studio.

Gebruikersnaam:
Onderwerp:

You can see runat=server is really in there so what's the problem?? Grtz Apoc