Firefox – Google search results greyed out on Firefox

If you pay attention to the status bar while hovering the link, you'll see that it initially points to the "clean" URL.

Only when you click on the link (with any of the three mouse buttons), a JavaScript event gets triggered that changes the link's destination to Google's URL redirection.

To verify my claim, just right-click any of the purple links and close the context menu. Unless you already visited the site from within Google's search results, you'll see that it changes colors.¹

I don't know exactly how Google injects the redirection URL², but the general idea is this:

// define a function `f' that changes a link's clean URL to a redirection URL
var f = function () {
    // prepend `http://www.google.com/url?rct=j&url=' to the link's target
    this.href = 'http://www.google.com/url?rct=j&url=' + escape(this.href);
    // don't invoke this function anymore when clicking the link
    this.removeEventListener('click', f);
    // don't invoke this function anymore when right-clicking the link
    this.removeEventListener('contextmenu', f);
}

// save all <a> tags in an array `a'
var a = document.getElementsByTagName('a');

// for each <a> tag in the array `a'
for (var i = 0; i < a.length; i++) {
    // execute function `f' when clicking the link
    a[i].addEventListener('click', f);
    // execute function `f' when right-clicking the link
    a[i].addEventListener('contextmenu', f);
}

You can try this jsFiddle to see how it works.

_{¹ Tested on Chromium 25 (Ubuntu 12.10) and Chrome 26 (Windows 7)}

_{² Minimized JavaScript is a bit difficult to read.}

I noticed using Fiddler that sending HTTP requests to Google would always return the 302s you mention, redirecting me to the HTTPS url as long as a Firefox user agent string was included in the request header. This is my current user agent string using Firefox 24 on Windows 7 x64:

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Firefox/24.0

So for me, a simple fix was to start using the User Agent Quick Switch add-on for Firefox. I changed my user agent string like this - just removed the Firefox/24.0 at the end:

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101

I'd guess a similar change to your Ubuntu user agent string would also do the trick, although there is an outside chance that it be problematic on another site.