function validateForm()
{
	var firstName = document.getElementById("first_name");
	
	if (firstName.value == "")
	{
		return invalidField("First name", firstName);
	}
	
	var lastName = document.getElementById("last_name");
	
	if (lastName.value == "")
	{
		return invalidField("Last name", lastName);
	}
	
	var email = document.getElementById("email");
	
	if (email.value == "")
	{
		return invalidField("Email address", email);
	}
	
	var atPos = email.value.indexOf("@");
	var dotPos = email.value.lastIndexOf(".");
	
	if (atPos < 2 || atPos == email.value.length - 1 || dotPos < 5 || dotPos > email.value.length - 3 || dotPos < atPos || email.value.indexOf("@", atPos + 1) != -1 || dotPos < atPos + 3 || email.value.indexOf(" ") != -1)
	{
		alert("Email address in not in a valid format.");
		
		return invalidField("", email);
	}
	
	var phone = document.getElementById("phone");
	
	if (phone.value == "")
	{
		return invalidField("Phone number", phone);
	}
	
	var validChars = "0123456789";
	
	for (var i = 0; i < phone.value.length; i++)
	{
		if (validChars.indexOf(phone.value.charAt(i)) == -1)
		{
			alert("Phone number in not in a valid format.");
			
			return invalidField("", phone);
		}
	}
	
	var comments = document.getElementById("comments");
	
	if (comments.value == "")
	{
		return invalidField("Comments", comments);
	}
	
	return true;
}

function invalidField(text, field)
{
	if (text != "")
	{
		alert(text + " is a required field.");
	}
	
	field.focus();
	
	return false;
}