a project is done in 2.0,how to convert that into 1.1, other than manually checking each line correcting to 1.1 coding, any ideas?

I don't envy you.  There's no tool available to do this, mainly because no one would choose to migrate in this direction.  That means it's a manual job, and could involve a lot of recoding.  The 2.0 Code-beside/behind model relies on Partial classes which weren't available in 1.1.  You'll need to refer to something like this to make sure you cover all the new features that were introduced in 2.9 that you need to revert: http://msdn.microsoft.com/en-us/library/fa1h9d0d(VS.80).aspx

It also begs the question why you would want to consider doing this.

one of my friend's client request.Thank for your reply.