Note: If you see a message saying you need to turn on Javascript in IE ( usually with SP2 ) go to Internet Explorer Menu, Tools >Internet Options, Click on the security tab, on the bottom either use default level, or click on Custom Level

Scroll down the list towards the bottom under the Scripting Catagory and turn on (enable) Active Scripting and Scripting of Java Applets. Without these options on, Javascript won't work. Note that Javascript is not the same as ActiveX, which poses known IE security risks.