Internet Explorer (IE), formerly Microsoft Internet Explorer (MIE), is a series of web browsers developed by Microsoft which has included as part of their Windows operating systems starting in 1995. While it was the dominant browser for many years, Microsoft announced on March 17, 2015 that Microsoft Edge would replace it as Microsoft's default browser. Internet Explorer version 11 was the last IE release. Which means that if you're on Windows 7 and have an earlier version if IE, it's time to upgrade.
It also means that you should take a hard look at the other popular browsers, such as Firefox and Chrome, and consider switching. If you are on a Macintosh, the time to switch is now - you can run IE 11 on a Mac if you are willing to do the technology equivalent of standing on your head, but there doesn't seem to be a good reason given the popular alternatives.
However, if you are on IE 11 and it is running slow, where a website may display "Page cannot be displayed" or "Cannot find server" error messages, with just a bit of housekeeping, you can resolve Internet Explorer performance issues and keep them from happening in the future. Here are some things to try