function toggleVisibility(tag, eClass, button, hideValue, showValue)
{
	spans = document.getElementsByTagName(tag);
	num=spans.length;
	for(i=0; i<num; i++)
	{
		if(spans[i].className==eClass)
		{
			visibility=getStyle(spans[i], 'visibility');
												
			if(visibility=="hidden")
			{
				spans[i].style.visibility="visible";
				button.value=hideValue;
			}
			else
			{
				spans[i].style.visibility="hidden";
				button.value=showValue;
			}
		}
	}
}

function getStyle(el, styleProp)
{
	if (el.currentStyle)
		var y = el.currentStyle[styleProp];
	else if (window.getComputedStyle)
		var y = document.defaultView.getComputedStyle(el,null).getPropertyValue(styleProp);
	return y;
}