ah, you said "one line" script
So, if you use FireFox:
1. right click on your bookmarks toolbar
2. select new bookmark
3. name it whatever you want (e.g. "nofollow checker")
4. paste this code into location input field
Code:
javascript:(function(){for (i = 0; i < document.links.length; i++) { if (document.links[i].rel && document.links[i].rel.indexOf('nofollow') != -1) { alert('This page uses *nofollow* links.'); break; } }})();
5. click OK & feel free to use it anytime you want