Your browser identified itself as a version of IE that was often shipped with default settings that were less than secure. Your internet experience could be made more secure by opening Internet Options in your browser, going to the Advanced tab and looking under the security settings for "Use TLS 1.1" and "Use TLS 1.2". Ensure these are turned on (checked). Doing so will enable your browser to support a higher quality of encryption on this and other websites. You will still be able to browse this site without turning on support for TLS 1.1 and 1.2, but we will have to use a lower level of encryption to accomodate you. See this question on Stack Exchange's Superuser forum from 2011 for more details keeping in mind the comments about TLS 1.2 non-support were made many years ago, and things have changed since then.
If the support for better cryptography has been turned on for your browser, thank you, and you can safely ignore this advisory.
Browser Security Alert