1) In internet explorer 11 , navigate to Tools –> Compatibility View Settings . Then add Domain name in the URL (ex: orapps.com in erp.oraapps.com) using Add this website option.
2) Navigate to Tools –> Internet options –> Security . Select internet and click on Custom level. Scroll down till end of the options and change the option Enable XSS filter to Disable.
This solution worked for me and I am able to open R12 forms in Internet Explorer version 11.
Restart Browser and Try again