I don't think I need to provide examples because every web developer knows that you need to test your Javascript to make sure it's compatible across different browsers. What I don't get is why. Isn't Javascript Javascript? It'd be like the .NET framework behaving differently on one computer than it does on another. Can anyone shed some light on this, possibly with some source links to go along with their answer?
Read this -> http://www.quirksmode.org/js/intro.html there are lots of version of the JavaScript implementation - all of them have differences.