base.consultant.ru/cons/static4000/ieonly.htm According to the link - the message of the Internet version of the Consultant when trying to work with the site through the latest version of FF.
I quote: To work in the systems ConsultantPlus: Internet requires a web browser Microsoft Internet Explorer 6.0 or higher running Microsoft Windows 98 / Me / NT / 2000 / XP.Please install it from here [link to Microsoft page].