Conditional comments are developed by Microsoft. And it only worked with IE browser. The conditional comments help to target IE browser & comments can be written to target the different version of IE 5-IE 9. CSS rules or code embedded inside of the comments will be used by an Internet Explorer based browser.  Whereas from IE10 & above, the support for conditional comments has been dropped.
According to the conditional comment this is not IE 5-9
A must-know for anyone heading into a CSS interview, this is frequently asked in CSS basic interview questions.