Where in the Bible...?

It's a common misconception that the serpent tricked Eve into eating the fruit from the tree. In reality, the temptation was put in front of her to eat the fruit, which she did. It's a lesson about the exercise of free will. Second, you're entirely correct that most people make the umption that the serpent is Satan. While there are corollaries in Revelation that refer to the serpent being struck down, I think it's a gross misread of that page. Serpents come in multiple incarnations throughout the Bible--not all of them literal. So to answer your question, I think that the view of serpent as Satan is not an error per se, merely a sort of origin and an embodiment of how evil works--as a sneaky, slithery menace that sometimes tempts you to do things that you would not otherwise do. Hope I've helped.