function is_valid(_lang) {
	var error_msg = "";

	var is_name = true;
	var is_address = true;
	var is_telephone = true;
	var is_email = true;
	
	if (document.getElementById("FORM_order_Nafn").value == "") {
		is_name = false;
	}
	
	if (document.getElementById("FORM_order_Heimilisfang").value == "") {
		is_address = false;
	}
	
	if (document.getElementById("FORM_order_Simi").value == "") {
		is_telephone = false;
	}
	
	if (document.getElementById("FORM_order_Netfang").value == "") {
		is_email = false;
	}

	if (is_name && is_address && is_telephone && is_email) {
		return true;
	} else {
		if (_lang == "en") {
			error_msg += "The following error(s) occurred:\n";
			
			if (!is_name) {
				error_msg += "- 'Name' is required.\n";
			}
			
			if (!is_address) {
				error_msg += "- 'Address' is required.\n";
			}
			
			if (!is_telephone) {
				error_msg += "- 'Telephone' is required.\n";
			}
			
			if (!is_email) {
				error_msg += "- 'Email' is required.\n";
			}
		} else if (_lang == "is") {
			error_msg += "Það komu upp eftirfarandi villur:\n";
			
			if (!is_name) {
				error_msg += "- 'Nafn' vantar.\n";
			}
			
			if (!is_address) {
				error_msg += "- 'Heimilisfang' vantar.\n";
			}
			
			if (!is_telephone) {
				error_msg += "- 'Sími' vantar.\n";
			}
			
			if (!is_email) {
				error_msg += "- 'Netfang' vantar.\n";
			}
		} else if (_lang == "de") {
			error_msg += "The following error(s) occurred:\n";
			
			if (!is_name) {
				error_msg += "- 'Name' is required.\n";
			}
			
			if (!is_address) {
				error_msg += "- 'Addresse' is required.\n";
			}
			
			if (!is_telephone) {
				error_msg += "- 'Telefon' is required.\n";
			}
			
			if (!is_email) {
				error_msg += "- 'Email' is required.\n";
			}
		} else if (_lang == "dk") {
			error_msg += "The following error(s) occurred:\n";
			
			if (!is_name) {
				error_msg += "- 'Navn' is required.\n";
			}
			
			if (!is_address) {
				error_msg += "- 'Addresse' is required.\n";
			}
			
			if (!is_telephone) {
				error_msg += "- 'Telefon' is required.\n";
			}
			
			if (!is_email) {
				error_msg += "- 'Email' is required.\n";
			}
		}
		
		alert ( error_msg );
		return false;
	}
}