This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Bear was hinting at your problem without saying it. The element needs to be removed from the body or the parent element. You either need to do document.body.removeChild(btn) or btn.parentNode.removeChild(btn);