function verifyPrice(input)
{ 
	if (input.value == "") {return true;}
  if (isNaN(Number(input.value))) 
   {
    alert ('Price must be a number, and cannot contain the characters "$" or ","');
    input.value = "";
    input.focus();return false;
   }
return true; 
}

function verifyMileage(input)
{ 
	if (input.value == "") {return true;}
  if (isNaN(Number(input.value))) 
   {
    alert ('Mileage must be a number, and cannot contain the character ","');
    input.value = "";
    input.focus();return false;
   }
return true; 
}

function verifyYear(input)
{
	if (input.value == "") {return true;}
	if (isNaN(Number(input.value))) 
	{ 
	 alert ('Year must be a number');
	 input.value = "";
	 input.focus();
	 return false;
	}
	if (input.value.length > 4)
	{
	 alert ('Year cannot be longer than 4 characters');
	 input.value = "";
	 input.focus();return false;
	}
return true;
}

function verifyAll(input)
{
	if (verifyYear(input.year) && verifyPrice(input.price) && verifyMileage(input.miles)) {return true};
	return false;	
}