Microsoft ending support for Internet Explorer 8, 9, and 10
Basically, they're going to stop offering security updates and technical help for these older versions of IE, apart from 11. Of course, running older versions means that, unless you're computer savvy, users could be more vulnerable to attacks on their computers.
"Regular security updates help protect computers from malicious attacks, so upgrading and staying current is important," Microsoft say. They'd like you to use IE 11 (or Edge), and they add that the newest version offers "improved security, increased performance, better backward compatibility" and other kinds of useful support.
Microsoft said this was going to happen back in August 2014, so this isn't a surprise, rather, a reminder.
There are some exceptions though - Microsoft have said that they're going to give help to enterprise customers (which are organisations with over 500 employees). With a lot of large companies slow to update their systems, Microsoft said that they'll be there to help them out.
However, if you're just someone with a computer in their house, running an older system, shortly, you'll be getting a final "End-of-Life" software update on the 12th, and that will have a prompt in it, to give you the opportunity to upgrade to a more recent browser.