function showRollover(thema) {
	if(document.getElementById) {
    hideRollover();
		var sRolloverDiv = thema + '_rollover';
		
		if (document.getElementById(sRolloverDiv).innerHTML.length == 0) return;
	  		document.getElementById('rollout_area').style.visibility = "visible";
			document.getElementById(sRolloverDiv).style.visibility = "visible";
	}
}

function hideRollover() {
	if(document.getElementById) {
		document.getElementById('schneeinfo_rollover').style.visibility = "hidden";
		document.getElementById('praevention_rollover').style.visibility = "hidden";
		document.getElementById('forschung_rollover').style.visibility = "hidden";
		document.getElementById('slf_rollover').style.visibility = "hidden";
		document.getElementById('dienstleistungen_rollover').style.visibility = "hidden";
		
		document.getElementById('rollout_area').style.visibility = "hidden";
	  }
}