function checknewsletterform()
				{					
				
					var str = "", msg = "";
					
					newsletter_mail = document.getElementById('newsletter_mail').value;
					
					if(newsletter_mail == "")
					{
						str = str + " - E-mailadres ontbreekt \n";
					}
					else if(!isValidEmail(newsletter_mail))
					{
						str = str + " - E-mail adres is onjuist \n";
					}	
					
					if(str != "")
					{
						msg = "De volgende gegevens ontbreken of zijn onjuist: \n \n"
						msg = msg + str;
						alert(msg);
						return false;
						
			
					}
					else 
					{
						document.getElementById('newsletter_form').submit ();
						return true;
						
					}											
				
				}
				
					function isValidEmail(email, required) {
						if (required==undefined) {   // if not specified, assume it's required
							required=true;
						}
						if (email==null) {
							if (required) {
								return false;
							}
							return true;
						}
						if (email.length==0) {  
							if (required) {
								return false;
							}
							return true;
						}
						if (! allValidChars(email)) {  // check to make sure all characters are valid
							return false;
						}
						if (email.indexOf("@") < 1) { //  must contain @, and it must not be the first character
							return false;
						} else if (email.lastIndexOf(".") <= email.indexOf("@")) {  // last dot must be after the @
							return false;
						} else if (email.indexOf("@") == email.length) {  // @ must not be the last character
							return false;
						} else if (email.indexOf("..") >=0) { // two periods in a row is not valid
						return false;
						} else if (email.indexOf(".") == email.length) {  // . must not be the last character
						return false;
						}
						return true;
					}
					
					function allValidChars(email) {
					  var parsed = true;
					  var validchars = "abcdefghijklmnopqrstuvwxyz0123456789@.-_";
					  for (var i=0; i < email.length; i++) {
						var letter = email.charAt(i).toLowerCase();
						if (validchars.indexOf(letter) != -1)
						  continue;
						parsed = false;
						break;
					  }
					  return parsed;
					}