function chkFormular()
{
 if(document.feedback.first_name.value == "")  {
   alert("The field Firstname is required!");
   document.feedback.first_name.focus();
   return false;
  }
 if(document.feedback.family_name.value == "") {
   alert("The field Familyname is required!");
   document.feedback.family_name.focus();
   return false;
  }
 if(document.feedback.email.value == "") {
   alert("The field Email adress is required!");
   document.feedback.email.focus();
   return false;
  }
}

function bw(bildname, bildtitel, autor)
{
 document.images.bild1.src = bildname + "_ss.jpg";
 document.f1.f_eins.value = bildtitel;
 document.f1.f_zwei.value = autor;
}
function clr()
{
 document.images.bild1.src = "../images/fotos/wtd03027_ss.jpg";
 document.f1.f_eins.value = "Participants of the first Warnemünde Turbulence Days";
}
function chkFormular()
{
 if(document.feedback.Filename.value == "")  {
   alert("The field Firstname is required!");
   document.feedback.first_name.focus();
   return false;
  }
  else {
  return true}
 }