I have made a website using(Asp.net, c#) and its content in English. Now i have a requirement to make this website in such a way that is su
Resx:
http://msdn.microsoft.com/en-us/library/ms227427.aspx
http://dreamdotnet.blogspot.com/2007/01/tutorial-translating-aspnet-web.html
You can use resx files for multiple languages and use the ResXResourceWrite to update them (if you want users to be able to update the files: http://msdn.microsoft.com/en-us/library/system.resources.resxresourcewriter.aspx)
This solution is only good for static content. If you want to be able to translate content from the database (for example if you have products stored in your database, and you want that the description of the product to be multilingual too). In this case you'll need to change you DB Scheme in order to support multilingual content.
PS
you can use GetLocalResourceObject("key")
in order to retrieve values without using web controls.
If you're using MVC, see the following question: How to localize ASP.NET MVC application?