function sichtbar(name) {
  var zz = document.getElementById(name);
  zz.style.visibility ='visible';
}

function unsichtbar(name) {
  var zz = document.getElementById(name);
  zz.style.visibility ='hidden';
}

function gehweiter(nextseite) {
var x = 0;
if(document.getElementById('see1').checked == true) {
	var x = 1;
}
if(document.getElementById('see2').checked == true) {
	var x = 2;
}
if(document.getElementById('see3').checked == true) {
	var x = 3;
}
/*
if(document.getElementById('see4').checked == true) {
	var x = 4;
}
*/
if(x > 0) {
 window.location.href=nextseite+'&sid='+x;
} else {
 alert ("Bitte wählen Sie erst einen See aus.");
}
}