Board Thread:Support Requests - Designing Your Wiki/@comment-26525672-20201010143938/@comment-9605025-20201011164142

The "-ms-" is called a vendor prefix. That means the property is not an official CSS property but one that a particular web browser (or web browser engine) decided to add on its own. This particular vendor prefix is for Internet Explorer. Other common vendor prefixes are "-o-" for Opera, "-moz-" for Firefox, and "-webkit-" for Safari, Chrome, and any other browser that uses Blink/Chromium (list of examples).