I\'ve a user control which contains asp:Literal.
It was very simple. I was adding things in web.config's controls section as was suggested by Rick Sthral in one of his post ( :( for got about the post, you will have to search on his page).
It was nicely allowing me to add controls without putting @ Register tag but the downside was that child controls on my controls were shown as null! so I simply put @ Register directive in my pages and it worked.