Comments are useful in CSS for two main reasons:

1. Writing Notes/Reminders to Yourself Inside of a CSS File
2. Temporarily Hiding Rules/Declarations While Testing a CSS File

CSS comments will be ignored by the browser, although they can be viewed in the source code.

Each comment begins with /* and ends with */ just like PHP multi-line comments. CSS comments can span multiple lines, and can appear inside or outside of rule sets.

/* This
is a
multi-line
comment. */

p {
  border: 1px dotted #000000;
  padding: 15px;
  /* margin: 25px; */
}