Puritube HTML Bookmarklet

<a  class="button"
    href="javascript:
        if(location.href.indexOf('youtube') !== -1) {
            location.href = 'http://puritube.com/' + location.href;
        } else {
            alert('This is not a valid YouTube video!');
        }"
    onclick="alert('To begin using the Puritube bookmarklet, please drag this button to the bookmarks toolbar of your browser.'); return false;"
>
        Puritube Bookmarklet
</a>