[Starson17]

Originally Posted by schuster

hi,
my problem today (i'm in lerning process with this stuff)
this recipe work's but in the mobi-book it shows me not the right things.
after a few hours of testing and trying i don't know the way

Spoiler:

class AdvancedUserRecipe(BasicNewsRecipe):

    title = 'National_Geo_test_6'
    description = '111beschreibung111'
    __author__ = 'irgendwer'
    publisher = 'jaja'
    language = 'de'
    oldest_article = 2
    max_articles_per_feed = 35
    no_stylesheets         = True
    use_embedded_content   = False
    remove_javascript      = True
    INDEX = 'http://www.nationalgeographic.de/archive/2008-05'
    def parse_index(self):
        articles = []
        soup = self.index_to_soup(self.INDEX)
        feeds = []
        for section in soup.findAll('div', attrs={'class':'searchresult_text'}):
            section_title = self.tag_to_string(section.find('headline-middle_no_margin black'))
            articles = []
            for post in section.findAll('a', href=True):
                url = post['href']
                if url.startswith('/'):
                  url = 'http://www.nationalgeographic.de'+url
                  title = self.tag_to_string(post)
                  if str(post).find('class=') > 0:
                    klass = post['class']
                    if klass != "":
                      self.log()
                      self.log('--> post:  ', post)
                      self.log('--> url:   ', url)
                      self.log('--> title: ', title)
                      self.log('--> class: ', klass)
                      articles.append({'title':title, 'url':url, 'section':section, 'section_title':section_title})
            if articles:
                feeds.append((section_title, articles))
        return feeds

    keep_only_tags = [dict(attrs={'class':['contentbox_no_top_border']})]

Kovid is right.
You are asking it to find a tag named 'headline-middle_no_margin black' when what you want is a tag named div with a class named 'headline-middle_no_margin black.' Look at your findAll on the line above the line defining section_title.
Try this:

section_title = self.tag_to_string(section.find('div', attrs={'class':'headline-middle_no_margin black'}))