Receptional_Andy - 11:16 pm on Apr 17, 2009 (gmt 0)

A proxy is not necessarily a client; public stealth proxies are servers and DO alter headers

I don't think we're going to agree about proxies ;)

As far as Google results goes, this is the way it's worked for a while:

- Google output the HTML of the results page
- In the HTML, links to results are plain old hrefs straight to the page
- A javascript function captures onclick events, and when you click on a result the script changes the destination to their own tracking URL
- Occasionally, Google hard-codes the click-tracking links in SERPs to go directly to the tracking URL (I assume to compare data with the javascript method, to make sure it's working adequately)

Google.com/url is the location of their click-tracking script. It grabs parameters in the URL for various purposes - mostly for tracking (the ranking and a few other bits and pieces - whether you clicked "did you mean?", which results page, etc).

There are also checksums that try to validate that they created the tracking URL, not you (otherwise you can hijack their redirect script, which was happening to them for a while). If the checksum doesn't match, you see a "we're sorry" page. It breaks if certain parameters aren't present, since it hasn't been programmed with an accurate response to that:

[google.com...]

If it's a valid URL, the script uses a location: response header, triggering a 302 HTTP redirect (with the effect of sending the browser to the actual result URL). The change is using javascript/meta refresh to redirect, instead of outputting a HTTP redirect. I think many would agree with me that this is generally seen as a unsatisfactory method of achieving a redirect.

Browsers don't typically update the referrer they send if they follow an HTTP redirect - they will usually use the prior URL as the referrer (perhaps because a redirect URL is not a good place to point people to). But javascript/meta redirects trigger a page load, and browsers may use that as the referrer they send instead.

But I'm inclined to think the referrer is just a side effect of the change, which is for some other reason. The click tracking script is nothing new (see [google.com...] for just a few of the posts about it). But tracking URLs showing up as the referrer certainly is.