scroll not working in ff

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Javascript

HTML

jQuery

Hi,

I want to make scrolling div. I am using this function to scroll div:

function ScrollUp() {
  document.getElementById('frameDiv').scrollTop +=30;
  return false;
}
function ScrollTop() {
  document.getElementById('frameDiv').scrollTop = 0;
}
function ScrollDown() {
  document.getElementById('frameDiv').scrollTop -= 30;
  return false;
}

but it's not working properly in FireFox.
Thanks.