I am new to .NET and  I have read what namespaces are.
  Now I am wondering when to use and when not to worry about namespaces. 
  From what I have seen, this is what I am thinking ?

     For website projects, I dont need namespaces so much. This is because website projects are in my dev environment, or on my
hosting file system environment.
Since they are on these environments, using a file/folder system works fine.
 Thirdparty dll's in my website projects have there own namespace schemes, so I dont have to worry to much about conflicts with
my website project elements.
  However, once I start creating code to be distributed, then, I will be using WAP projects. In this case, I will be using
namespaces and creating dll's. Because these will be
distributed, I now need namespaces so I dont collide with other file/folder names in other peoples environments, or other
application environments, like DNN. 

Yes, that's right.

thanks Joseph