function enableTab(tab_id)
{
	if(document.getElementById(tab_id))
	{
		document.getElementById(tab_id).className = "active";
	}
	else
	{	
		document.getElementById("tab_home").className = "active";
	}
}

function markFieldAsError(field_id)
{
	if(document.getElementById(field_id))
	{
		document.getElementById(field_id).className = "error";
	}
}