function check_form() 
{
    error_message = "";

    if (!IsZipcode(document.getElementById('customer_address_zip_input').value))
        error_message += "Please enter a valid zip code.\n";
	
	if (!document.getElementById('existingCoverage_1').checked && !document.getElementById('existingCoverage_0').checked) {
		error_message += "Please choose 'yes' or 'no' to answer the question 'do you have car insurance?' \n";
	}
	
    if(error_message != "") 
    {
        error_message = "Please Fix the following Field(s):\n\n" + error_message;
        alert(error_message); 
        return false; 
    } 
    
    return true; 
}