function validate_form(form){ 
  field_comments = white_space(document.getElementById('comments')); 
  field_name = white_space(form.name);  
  field_email = white_space(form.email); 
  field_phone = white_space(form.phone); 
   
  if(field_name.length < 2 || form.name.value=="Your name"){ 
    alert("Your name is not valid"); 
    return false; 
  } 
  if(!isValidEmail(field_email) || form.email.value=="Your email"){ 
    alert("Email address is not valid."); 
    return false; 
  } 
  
  if(field_phone.length < 8 || form.phone.value=="Your phone number"){ 
    alert("Phone number is not valid."); 
    return false; 
  } 
  if(field_comments.length < 1 || field_comments=="Your enquiry"){ 
    alert("Web message is not valid"); 
    return false; 
  } 

  return true;
} 

function white_space(field) 
{ 
  return (field.value).replace(/^\s*/g,''); 
} 

function isValidEmail(str){ 
  return (str.indexOf(".") > 2) && (str.indexOf("@") > 0); 
}