require 'rubygems'
require 'rubyful_soup'
invalid_html = 'A lot of <b class=1>tags are <i class=2>never closed.'
soup = BeautifulSoup.new(invalid_html)
puts soup.prettify

A lot of
<b class="1">tags are
<i class="2">never closed.
</i>
</b>

A lot of 
  <b class="1">tags are 
   <i class="2">never closed.
   </i>
  </b>

soup.b.i

soup.i

soup.find(nil, :attrs=>{'class' => '2'})

soup.find_all('i')

soup.b['class']

soup.find_text(/closed/)

require 'rubygems'
require 'html/sgml-parser'
require 'set'
html = %{<a name="anchor"><a href="http://www.oreilly.com">O'Reilly</a>
         <b>irrelevant</b><a href="http://www.ruby-lang.org/">Ruby</a>}
class LinkGrabber < HTML::SGMLParser
  attr_reader :urls
  def initialize
    @urls = Set.new
    super
  end
  def do_a(attrs)
    url = attrs.find { |attr| attr[0] == 'href' }
    @urls << url[1] if url
  end
end
extractor = LinkGrabber.new
extractor.feed(html)
extractor.urls

require 'rubyful_soup'
urls = Set.new
BeautifulStoneSoup.new(html).find_all('a').each do |tag|
  urls << tag['href'] if tag['href']
end
puts BeautifulStoneSoup.new(html, :parse_only_these => 'a')

<a name="anchor"></a>
<a href="http://www.oreilly.com">O'Reilly</a>
<a href="http://www.ruby-lang.org/">Ruby</a>

<a name="anchor"></a><a href="http://www.oreilly.com">O'Reilly</a><a href="http://www.ruby-lang.org/">Ruby</a>