Link tag

<link href="http://fonts.googleapis.com/css?family=Open+Sans" rel="stylesheet" type="text/css" />

CSS import

/* One font */
@import url('https://fonts.googleapis.com/css?family=Open+Sans:400,700');

/* Combining multiple fonts */
@import url('https://fonts.googleapis.com/css?family=Open+Sans:400,400italic|Montserrat:400,700'');

Great for using with Codepen.io or similar websites!