One of the customers are facing difficulty while logging into our webiste, whenever the user types the first character in UserName text box on the sign in page, he gets below JavaScript error message.

Unable to get value of property 'keyCode': object is null or undefined

We do check for event.keyCode to validate the userName textbox , so as soon as the user types the first character we send the event.keyCode for validation which is failing.

The browser is internet Explorer 9 and we are not able to reproduce the problem in our workstation which has I9