... in it, it will not be considered (and this could cause major issues if you had in-line comments), and all white space is removed, except the single space, preventing non-white space in plain text. Also, if your css3 command starts with "@", it will need to be all in one line. (example: @keyframes ___{} must all be on a single line.) However, it will increase support, and reduce the file size, so that when many people visit your website, you use less data and have more functionality for more people.