I am using less.js to compile less on the fly. Here's a sample of my markup:
<html>
<head>
<link rel="stylesheet/less" href="sample.less" type="text/css" />
<script src="http://cdnjs.cloudflare.com/ajax/libs/less.js/1.7.4/less.min.js"></script>
</head>
<body>
<div class="box">
abcd
</div>
</body>
</html>
It is not compiling less into CSS: