Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical supports and security updates. Internet Explorer 11 is the last version of Internet Explorer, and will continue to receive security updates, compatibility fixes, and technical support on Windows 7, Windows 8.1, and Windows 10.

Internet Explorer 11 offers improved security, increased performance, better backward compatibility, and support for the web standards that power today’s websites and services. Microsoft encourages customers to upgrade and stay up-to-date on the latest browser for a faster, more secure browsing experience.
It means you should take action. After January 12, 2016, Microsoft will no longer provide security updates or technical support for older versions of Internet Explorer. Security updates patch vulnerabilities that may be exploited by malware, helping to keep users and their data safer. Regular security updates help protect computers from malicious attacks, so upgrading and staying current is important.
https://www.microsoft.com/en-us/WindowsForBusiness/End-of-IE-support

Given that, if you are on IE10, please upgrade. I will stop testing on IE10 with upcoming feature sets, especially when it comes to CSS.
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