Is it a good design to have multiple masterpages in an application. I am building a website using Asp.net MVC with different type of users like, admin, employee, general user, etc
And every user once logged in have different type of controls on the website, so I was planning to use different master page for each user.
Yes it is a good design, and make sure to layer them appropriately. Master pages specific to controllers should be placed them in the appropriate view folder.
Also, check out http://blog.codeville.net/2008/10/14/partial-requests-in-aspnet-mvc/ for a way to make "widgets" from partial views.
If it makes life easier for you and your users, than I see no reason why not.
why can't we use single master page in our common applications with multiple users?