function validateForm()
{
var error_fields = new Array();

var name = document.getElementById('el_1');
var email =  document.getElementById('el_2');
var anfrage = document.getElementById('el_3');

if(name.value == "")
{
error_fields[error_fields.length] = "Name";
var labelId = "label-" + name.id;
document.getElementById(labelId).style.color = "#f11";
}

var posAtSign = email.value.indexOf("@");
alert
if(email.value == "" || posAtSign == -1 || posAtSign == 0 || posAtSign == (email.value.length-1))
{
error_fields[error_fields.length] = "E-Mail";
var labelId = "label-" + email.id;
document.getElementById(labelId).style.color = "#f11";
}

if(anfrage.value == "")
{
error_fields[error_fields.length] = "Ihre Nachricht";
var labelId = "label-" + anfrage.id;
document.getElementById(labelId).style.color = "#f11";
}

if(error_fields.length != 0)
{
var error_content = "Bitte geben Sie für folgende Felder gültige Werte ein:\n";
error_content += error_fields.join("\n");
alert(error_content);
return false;
}
else
{
var email_confirm= confirm("Ist die E-Mail-Adresse "+ email.value  + " korrekt?\nBitte beachten Sie, dass wir auf Ihre Anfrage nur antworten können, wenn Sie eine korrekte E-Mail-Adresse angeben.");
if (email_confirm== false)
{
return false
}
return true;
}
}

window.onload  = function()
{
var form_elem = document.getElementById('contact-form');
if(form_elem != null)
{
form_elem.onsubmit = validateForm;
}
}