SCSS mixins

A mixin lets you make groups of CSS declarations that you want to reuse throughout your site. You can pass in values to make your mixin more flexible.

Here's an example for border-radius.
@mixinborder-radius($radius) {
  -webkit-border-radius: $radius;
     -moz-border-radius: $radius;
      -ms-border-radius: $radius;
          border-radius: $radius;

.box { @includeborder-radius(10px); }
The generated CSS looks like:
.box {
  -webkit-border-radius: 10px;
  -moz-border-radius: 10px;
  -ms-border-radius: 10px;
  border-radius: 10px;

For more information on Sass, see the Sass/SCSS reference.