(Referenceerror): 'his' is undefined

Question

Hi all, 
 we are using Appian 7.10 and when one of the user tried to access a page and clicking on a button, it is throwing a pink box error (Referenceerror): 'his' is undefined. but we are not using any function or variable called "his". And the same is working for other users in the same group. Did anyone faced similar kind of issue. Any help would be appreciated. 
 thanks in advance

Muneer Varma · Answer

Thanks for your response, this user was able to access the page earlier. The issue is fixed. We changed the IE compatibility(document) mode from 9 to 10 and it started working. But the strange thing is the application is working fine with IE compatibility mode of 9 for almost all the users. only one user had the issue.