How you deployed it? Using Publish method? or Simply Copy - Paste all the Project folder contents to server?
Check these links :
http://forums.asp.net/p/1181651/2006021.aspx
http://bytes.com/groups/net-asp/571466-compiler-error-message-cs0246-type-namespace-name-could-not-found-you-missing-using-directive-assembly-reference
http://stackoverflow.com/questions/89570/appcode-folder-issues
http://social.msdn.microsoft.com/Forums/en-US/asmxandxml/thread/af5d0e78-8214-4a68-9980-e3aad7dfcbe9/
Thanks
Anuraj P
http://www.dotnetthoughts.net
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BEWARE OF BUGS IN THE ABOVE CODE; I HAVE ONLY PROVED IT CORRECT, NOT TRIED IT.