function showPreviousRates()
{
if (document.getElementById('currentRates')  != null) document.getElementById('currentRates').style.display  = 'none';
if (document.getElementById('previousRates') != null) document.getElementById('previousRates').style.display = 'block';
}

function showCurrentRates()
{
if (document.getElementById('currentRates')  != null) document.getElementById('currentRates').style.display  = 'block';
if (document.getElementById('previousRates') != null) document.getElementById('previousRates').style.display = 'none';
}