login control password

There is many way to do so.
One of it is that you have to add two textBox for your password field.
Keeping one of your password field visibility to false initially in your form activates only one textbox to the user where they can enter their Password.
Now save the password in a string variable in the TextBoxChange event.
Now you in CheckBox Change event store the password variable in your another textbox whose visibilty was kept hidden initially, after that hide the first textbox in which user has inputted their password and show the another textbox whose visibility was kept hidden initially.
Thats it you get the password visible.
Looking Confused here is the source code for this.
Its very simple you can download it.
I am giving the Source Code for Windows Form Application.
You can however implement it in your Web application(ASP.net) easily.

it depends upon from where you have show password into the control that is from data base or other but you can write code on selected changed event of check box and set Autopostback property of checkbox to true