Could not load file or assembly 'MySql.Data, Version=6.6.5.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The system cannot find the file specified.

hi, everyon i m a new webdeveloper, i hosted a website in server and i m getting error," Could not load file or assembly 'MySql.Data, Version=6.6.5.0, ". when i run this applicatin in asp.net version 4.0  its ok, no errror i m getting, but on server i m getting this error.plz help.
thank you.