.btn-b {
    @include verticalGradient(white, lighten($beautifulHue, 30%));
}

.btn-b {
    @include verticalGradient(white, $beautifulHue);
}

@mixin verticalGradient($fromColor, $toColor) {
    background-color: $toColor;
    background-image: -moz-linear-gradient(top, $fromColor, $toColor);
    ...
    background-image: linear-gradient(to bottom, $fromColor, $toColor);
}
.btn-b {
    @include verticalGradient(blue, red);
}

.btn-a {
    background-color: lighten($beautifulHue, 45%);
}

a {
    color: $beautifulHue;
}
@import 'header';
.btn-a {
...

.btn-a {
    display: inline-block;
    padding: 10px;
}
.btn-b {
    @extend .btn-a;
    background-color: black;
}

.btn-a, .btn-b {
    display: inline-block;
    padding: 10px;
}
.btn-b {
    background-color: black;
}

headers

expires

sudo a2enmod headers 
sudo a2enmod expires

service apache2 restart

.htaccess

# for enabling browser caching
<filesMatch ".(css|jpg|jpeg|png|gif|js|ico)$">
Header set Cache-Control "max-age=2592000, public"
</filesMatch>

$("#element").keyup(function(event){
    if(event.keyCode == 13)
        someAction('param');
    }
});