a simple mixin file sample

_mixins.scss

@mixin box-shadow( $shadow ) {
  -webkit-box-shadow: $shadow;
     -moz-box-shadow: $shadow;
          box-shadow: $shadow;
}
@mixin linear-gradient( $start, $stop1, $stop2 ) {
  background-image: -webkit-linear-gradient( $start, $stop1, $stop2 );
  background-image:    -moz-linear-gradient( $start, $stop1, $stop2 );
  background-image:     -ms-linear-gradient( $start, $stop1, $stop2 );
  background-image:      -o-linear-gradient( $start, $stop1, $stop2 );
  background-image:         linear-gradient( $start, $stop1, $stop2 );
}
@mixin box-sizing( $box-size ) {
  -webkit-box-sizing: $box-size;
   -khtml-box-sizing: $box-size;
    -icab-box-sizing: $box-size;
     -moz-box-sizing: $box-size;
       -o-box-sizing: $box-size;
          box-sizing: $box-size;
}