Error: “Sys” is Undefined Error

This is an javascript error will display in the browser because of some references missing in web.config file of your application and specially when you host your application to the server.
To resolve this please follow the below steps
1. Open the web.config file
2.Copy the below code to inside of

Http handlers are the .NET Components that implement the System.Web.IHttpHandler.
They are similar to ISAPI extensions,but one difference is the Http handles can be called directly by using their file name in the URL.
3.Copy the below code inside of

HTTP modules are .NET components that implements the System.Web.IHttpModule interface.
They are plug into the ASP.NET request processing pipeline by registering themselves for certain events