function replace()
{
	var left = document.getElementById("colLeft");
	var leftNum = left.getElementsByTagName('img').length;
	
	if(leftNum == 0)
	{
		left.innerHTML = '<img src = "http://www.hold.mx/wp-content/themes/hold/images/izquierda.jpg" style = "margin-top:200px" />';
	}

	var right = document.getElementById("colRight");
	var rightNum = right.getElementsByTagName('img').length;
	
	if(rightNum == 0)
	{
		right.innerHTML = '<img src = "http://www.hold.mx/wp-content/themes/hold/images/derecha.jpg" style = "margin-top:200px" />';
	}
}