The one and only way to comment in CSS is using /* comment here */.
/* Multiline Comment: - add more css later*/.content { line-height: 1em; /* comment again */}No single line comment
Single line comment like // please don't comment like this is not recommended. Though it won't break CSS in some cases, but you will bump into issues when the CSS is minified.
.content { line-height: 1em; // please don't comment like this}No nested comment
One of the limitation with CSS comment is you can't do nested comment.
/* nested comment won't work.content { line-height: 1em; /* nested comment */} */Less and Sass
You might consider Less and Sass if you want to support single line comment and nested comment.