function changeCheckboxSelection(form, checkname, arg) {
  if(arg == 1)
    for (i = 0; i < form.elements[checkname].length; i++)
    	form.elements[checkname][i].checked = true;
  if(arg == 0)
	for (i = 0; i < form.elements[checkname].length; i++)
	    form.elements[checkname][i].checked = false;
  if(arg == -1)
	for (i = 0; i < form.elements[checkname].length; i++)
	    form.elements[checkname][i].checked = (form.elements[checkname][i].checked == true ? false : true);

}

function showHeaderSubText() {
	var elm = document.getElementById("header_subtext");
	if (elm)
	  elm.style.display = "block";
}

function hideHeaderSubText() {
	var elm = document.getElementById("header_subtext");
	if (elm)
	  elm.style.display = "none";
}


function del_login_text() {
  if(document.getElementById('login_benutzername').value == "E-Mail-Adresse")
    document.getElementById('login_benutzername').value = "";
}