It is personal preference, double quotes are also acceptable. Keep in mind that if there is a space separating two individual values then you need to wrap them in quotes:
@Joshuan, that is in HTML. In HTML5 it is valid to use no quotes, but I recommend to use them. Because of the space problem.
@Cybershot, in CSS there is no need to use quotes. But it has the same problem as in HTML, if there is a space you need to use de quote. Examples:
font-family: 'Trebuchet MS', Verdana, sans-serif; /* Trebuchet MS needs quotes, because there is a space in the name */ background: url('images/my image.png'); /* There is a space => quotes (but in this case, I should remove the space in the name */ background: url(images/myimage.png); /* No spaces, so we don't need to use quotes */
background: url('images/myimage.png');
or
background: url(images/myimage.png);
class=banner ribbonIs not equal to:
class="banner ribbon" or class='banner ribbon'@Cybershot, in CSS there is no need to use quotes. But it has the same problem as in HTML, if there is a space you need to use de quote. Examples: