Hi Harshraj,
Look here for the solution:
https://academy.mendix.com/link/modules/183/lectures/1419/3.4-Custom-Login-Page
Go Make IT
not sure if this helps you:
there are 2 ways for users to login.
http://localhost:8080/index.html
http://localhost:8080/login.html
one is a HTML page with no connection to your mendix application.
the other is a page within mendix.
there seems to be some confusion between the 2 sometimes.