function validate_email(field)
{
	apos = field.value.indexOf("@");
	dotpos = field.value.lastIndexOf(".");
	return (!(apos < 1 || dotpos-apos < 2));
}

function checkcontactformulier()
{
	for(i = 0; i < 11; i++)
	{
		
		box = document.getElementById("contactformulier").elements[i];

		switch(i)
		{

				case 6:
					if (!validate_email(document.getElementById("contactformulier").elements[6]))
					{
						alert('Vul een geldig e-mail adres in. Please fill in a valid email address.');
						document.getElementById("contactformulier").elements[6].focus();
						return false;
					}
					break;
				
				default :
					if (!box.value)
					{
						alert('Vul alle verplichte velden in. Please fill in all required fields.');
						box.focus()
						return false;
					}
					break;
		}
	}

	return true;
}