Normally, the referrer is traceable through:
document.referrer
$_SERVER[\'HTTP_REFER
As requested, by using JavaScript:
var meta = document.createElement('meta');
meta.name = "referrer";
meta.content = "no-referrer";
document.getElementsByTagName('head')[0].appendChild(meta);
This will add the following meta tag to head section of the web page:
As of 2015 this is how you prevent sending the Referer header.