A sample code of the Watir. This automates 緑のgoo's "水をあげる"

midori_no_goo_watir.rb

#! ruby
# coding: utf-8

require "rubygems"
require "watir-webdriver"

browser = Watir::Browser.new :firefox, :profile => "default"
browser.goto "http://green.goo.ne.jp/"
btn = browser.div(:id => "tree").div(:class => "btn").images[0]
div = browser.div(:id => "tree").ul(:class => "clearfix").li(:class => "count").divs[2]
count = div.class_name.scan(/\d+\Z/)[0].to_i

count.times do
  until btn.src =~ %r!/mytree_btn_water.jpg! do end
  btn.click
end