It's not "doing nothing", it's throwing an exception because you're trying to access a property of a null object. You're calling document.getElementById() correctly, so the problem is that the id ...

Note the capital B. This caused me (a non-js user) to flounder around for 20 minutes looking for what the problem was. Sorry if I'm submitting this in the wrong place.

JavaScript Cannot Get Elements From an iFrame. Retrieving elements from an iFrame can be complicated process due to cross-browser incompatibility. While one method might work for a user accessing ...