If you receive an email asking you to "sign" a petition, it is probably a hoax. Email hoaxes are as common as spam and include petitions, chain letters, and advance fee fraud (i. e., the Nigerian Scam). One such hoax that has seen renewed activity in light of the U. S. military actions taken in Afghanistan is the "Women in Afghanistan" petition. Whether the issues behind the petition are full of misinformation, or as in this case, are fairly accurate, online petitions don't help anyone. Learn more about hoaxes here: http://www.snopes.com/inboxer
Learn about the Women in Afghanistan Petition here: http://www.snopes2.com/inboxer/petition/afghani.htm