I'm gonna put an example using BeautifulSoup, a Python module which we can parse HTML.

First we've to download the library from here. Once installed, let's see the simple example:

 
from BeautifulSoup import BeautifulSoup
 
html = '''<html><head><title>Titulo de la pagina</title></head>
  <body>
<div id="cabecera">
<h1>Cabecera</h1>
</div>
<div id="contenido">
    Vamos a poner una lista.
 
    Lista:
<ul id="lista1">
<li>Elemento 1</li>
<li>Elemento 2</li>
<li>Elemento 3</li>
<li>Elemento 4</li>
</ul></div>
 
  </body>
  </html>'''
 
soup = BeautifulSoup(html)
 
# Mostramos el titulo de la pagina
print soup.head.title.string
 
# Mostramos la cabecera
print soup.find("div",{"id":"cabecera"}).contents
 
# Mostramos el contenido
contenido = soup.find("div",{"id":"contenido"})
print contenido.contents
 
# Ahora mostramos todos los elementos de lista1
lista = contenido.find("ul",{"id":"lista1"})
for x in lista:
    print x.string
 

Instead of a string with html code we can read from an URL on this way:

 
...
import urllib2
 
sock = urllib2.urlopen("http://servidor/documento.html")
soup = BeautifulSoup(sock.read())
...
 

It's a very simple sample, for details read the BeautifulSoup documentation.