Recently I asked some questions about code behind. I received some helpfull answers, but I was not realy satisfied yet.
So I also asked microsoft also. It made a lot clear to me.
So for all the people who are also new to ASP.NET (like me)
it is time for me to share:

1. When you use VS your files are automaticly devided into
html files (aspx) and code behind files (aspx.vb or .cs) I use .vb

2 At design time your html (aspx) page has a "propertie" code behind. It refers to your aspx.vb files. When you run your application at designtime it looks at these "code behind " to compile your "code behind" at runtime.

3. When you build a solution one big dll is created at the bin directory of your application.

4. When you want to deploy your application, you can 'erase' all your aspx files, because your aspx files do not use your "codebehind" property any longer. Instead of that it now uses the "inherit" property. It refers to your dll in the bin directory and the classname.

Because the codebehind still refers to the aspx.vb it is a little bit confusing.

5. You can allso create your own dll, by compiling a vb modul with vbc.exe and put it in the bin directory of your application. In the aspx module you can refer to the dll (with the inherits property)

good luck,

Krol