Selenium has one webdriver instance per session

This way different sessions can have different
options

lib/capybara/driver/selenium_driver.rb

@@ -81,14 +81,14 @@ class Capybara::Driver::Selenium < Capybara::Driver::Base
 
   attr_reader :app, :rack_server
 
-  def self.driver
-    unless @driver
-      @driver = Selenium::WebDriver.for :firefox
+  def browser
+    unless @browser
+      @browser = Selenium::WebDriver.for :firefox
       at_exit do
-        @driver.quit
+        @browser.quit
       end
     end
-    @driver
+    @browser
   end
 
   def initialize(app)
@@ -127,10 +127,6 @@ class Capybara::Driver::Selenium < Capybara::Driver::Base
     browser.execute_script "return #{script}"
   end
 
-  def browser
-    self.class.driver
-  end
-
   def reset!
     browser.manage.delete_all_cookies
   end