function showme(a) {
document.getElementById('strom-h').className = 'tr-head';
document.getElementById('kombi-h').className = 'tr-head';
document.getElementById('gas-h').className = 'tr-head';
document.getElementById(a+'-h').className = 'tr-head-a';
document.getElementById('strom').style.display = 'none';
document.getElementById('gas').style.display = 'none';
document.getElementById('kombi').style.display = 'none';
document.getElementById(a).style.display = 'block';

}