Instalar o usar XPATH en Ruby

Buenas alguien me pordia explicar como instalar o usar xpath en ruby.
estoy tratando de hacer uso de este código:

Código:

browser.link(:xpath, "//a[@href='web3.htm']/").click

y me devuelve este error

Código:

C:/Ruby193/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.9-x86-mingw32/lib/nokogiri/xml/node.rb:159:in `evaluate': Invalid predicate: //a[@href='web3.html')]/ (Nokogiri::XML::XPath::SyntaxError)
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.9-x86-mingw32/lib/nokogiri/xml/node.rb:159:in `block in xpath'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.9-x86-mingw32/lib/nokogiri/xml/node.rb:150:in `map'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.9-x86-mingw32/lib/nokogiri/xml/node.rb:150:in `xpath'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/xpath_locator.rb:34:in `elements_by_xpath'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/locator.rb:112:in `locate_elements_by_xpath_css_ole'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/locator.rb:146:in `locate'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/element.rb:308:in `locate'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/element.rb:325:in `assert_exists'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/element.rb:474:in `perform_action'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/element.rb:354:in `click!'
	from C:/Ruby193/lib/ruby/gems/1.9.1/gems/watir-classic-3.6.0/lib/watir-classic/element.rb:157:in `click'
	from C:/Documents and Settings/Administrador/Escritorio/link.rb:20:in `<main>'
[Finished in 4.9s with exit code 1]

mi html la parte que quiero obtener seria esta:

Código:

<a href="web3.htm"></a>

Por favor ayudaaaa!!!