Code to Get Contents of iFrame (cross browser)

I need a javascript function that gets the contents of an iFrame. This is in response to an onload function that is kicked of when the src of the iFrame changes. // Function returns string function GetContents() { // iFrame ID is 'answertext' } This will work within the same domain, therefore the security model should support it. It must support at the very least IE, FF, and Chrome.