Run LESS in JSFiddle

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/less.js/1.7.0/less.min.js"></script>
<input placeholder="text">

CSS

::-moz-placeholder {
 color:red;
}

::-webkit-input-placeholder {
 color:red;
}

JavaScript

$('head style[type="text/css"]').attr('type', 'text/less');
less.refreshStyles();