use of y and en in french and pronouns

• http://french.about.com/od/grammar/a/pron_adverbial.htm
• http://french.about.com/od/grammar/a/pronouns_demonstrative.htm
• http://french.about.com/od/grammar/a/pronouns.htm
• http://french.about.com/od/grammar/a/pronouns_2.htm
• http://french.about.com/lr/french_pronouns/1436208/1/