Firefox Quantum (57+) users: Install the Violentmonkey extension or Tampermonkey extension from Mozilla Add-ons BEFORE installing this userscript. The script might also work in the Greasemonkey extension.
Firefox 45-56 users: Install a legacy version of the Greasemonkey extension from Mozilla Add-ons BEFORE installing this userscript.
Other Browsers: I honestly have no idea.
Want to limit your query to a particular site in the results? Or to re-run the query excluding that site from the results? Click the green citation URL below the result header to display a form. It should be self-explanatory from there, but see the screen shots below for an example.
For a more detailed description, check out Ann Smarty's article 3 FireFox Addons to Use Google's SITE: More Effectively at ShimonSandler.com. Apologies for obsoleting the screen shot so quickly!
The script makes the green citation clickable:
You may have choices of directories on the site in addition to the main domain.
Click the + button to limit your query to this site, or the - button to exclude the domain. This dialog also has a checkbox to change script options (click Edit Script Options).
Result of + button:
Result of - button:
The script detects the "title and date" format in results, indents it, and adds a link for More Results:
By default, the script adds "more results from" links but these open in the same window or tab. You can check a box in options to open them in a new wndow or tab. Also, by default, the script shows the domain without www as the first option. If you always want to drop the first subdomain, there now is a checkbox for that (e.g., productforums.google.com and groups.google.com could be omitted by omitting google.com). This feature may offer nonsense choices in multi-level TLDs (e.g., co.uk).
v1.4.0 Emergency fix for Google putting the cite inside the result link (may be slightly buggy)
v1.3.0 Added GM.getValue and GM.setValue code to support Greasemonkey 4(alpha)
v1.2.0 Change .tld to .* for Tampermonkey