Is Jacopo di Poggibonsi real

No, Jacopo di Poggibonsi is an fake person created by people from this website (http://www.saskschools.ca/~ischool/tisdale/integrated/wysiwyg/teacher.htm) to get children to understand that not everything they read on the internet is true. So, I presume that you are a child and your teacher has told you to find information out about Jacopo di Poggibonsi. Go and tell her (and the rest of the class) that he is a fake person and does not exist.