function checkRequiredFields(input)
			{
			var x = document.forms[0].email.value;
			var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

			var requiredFields = new Array("naam",
			"adres",
			"postcode",
			"plaats",
			"telefoon",
			"email");
			var fieldNames = new Array(	"Naam",
			"Adres",
			"Postcode",
			"Plaats",
			"Telefoonnummer",
			"E-mail adres");
			var fieldCheck   = true;
			var fieldsNeeded = "\nDit contactformulier bevat een aantal verplichte velden. \nVult u aub de volgende ontbrekende velden in:\n\n\t";

			for(var fieldNum=0; fieldNum < requiredFields.length; fieldNum++) {
			if ((input.elements[requiredFields[fieldNum]].value == "") ||
			(input.elements[requiredFields[fieldNum]].value == " ")) {

			fieldsNeeded += fieldNames[fieldNum] + "\n\t";
			fieldCheck = false;
			}
			}

			if (fieldCheck == true)
				{

				if (filter.test(x)) {return true;}
					else
					{alert('Geen geldig e-mail adres!');
					return false;
				}
			}
			else
			{
			alert(fieldsNeeded);
			return false;
			}
			}