Google Click tracking feature secretly tracks which URL on the web results page was clicked by the user. The Google Privacy policy states that Google use this click information to improve the quality of search technology, customized content and advertising.

Google is using this click data to refine their search results and pagerank based on which webpages are popular with users and which links are clicked most frequently by Google Users. Yet the Google Click Tracking feature has been a concern for many privacy advocates.

A normal web user is unaware that he is being redirected and the URL text shown in green on the Google search results page is very different from the page title URL that he just click. Google reformats the destination URL so that the click is redirected through Google servers.

How Google Tracks search clicks (or visits) ?

Google embeds a small javascript function in the search results page that redirects any user click via Google webservers.

function rwt(el,ct,cd,sg)
{
var e = window.encodeURIComponent ? encodeURIComponent:escape;
el.href="/url?sa=t&ct="+e(ct)+"&cd="+e(cd)+"&
url="+e(el.href).replace(/\+/g,"%2B")+"&ei=f3NCROGdD6f2qwKh8qT8BA"+sg;
el.onmousedown="";return true;
}

The above javacript rewrites a URL like http://labnol.blogspot.com to something like below:

http://www.google.com/url?sa=t&ct=res&cd=1& url=http%3A%2F%2Flabnol.blogspot.com%2F&ei=f3NCROGdD6f2qwKh8qT8BA &sig2=acgf-_t9eoqUbkKqkoFCfg

Clearly, the web searcher is not aware that he is actually clicking a different URL. Second if one wants to copy the destination URL to the clipboard by right clicking and saying "Copy Link Location" - all you get on the clipboard is this cryptic URL. Either wear lenses and remove all those geeky characters surrounding your URL or better, just copy the text in green on the Google web search results page and append http://.

If you're on Firefox, get the CustomizeGoogle plug-in and it blocks Google from tracking your click-through information. Here's what the extension does internally:
	
removeUrlClickTrack: function() {
var match = null;
var a = selectAllNodes(document,document.body,"//a");
for (var y=0; y< a.length; y++) {
match = a[y].href.match(/^(http:\/\/www\.google|\/url).
+?q=(http:[^&]+)/i);
if (match) { a[y].href = unescape(match[2]); }
a[y].onmousedown = function() { return true; }
}},
The logic is to take the Google URL if matches the form www.google.com/url and replace it with the value of URL parameter. Neat. It works.

Yahoo click tracking mechanism generates an even more complex web URL but it is much simpler - the URL is appended at the end of the URL.

Google Click tracking is anonymous and uses no cookies. It is also different from Google Search History which shows Personalized Search results.