function select_tab(id,aantal)
{
	for(i = 1; i <= aantal; i++)
	{
		if (i == id)
		{
			document.getElementById('tab_'+i).style.backgroundPosition = "0px 54px";
			document.getElementById('tab_content_'+i).style.display = "";
		}
		else
		{
			document.getElementById('tab_'+i).style.backgroundPosition = "0px 0px";
			document.getElementById('tab_content_'+i).style.display = "none";
		}
	}
}