title: Trying to validate captcha with javascript before sending to php form validation
body: <p>Hi I'm a relative newbie. 
  Have a mail contact form set up with a captcha image generator.
  When the captcha is verified, on submitting the form, a php page is actioned which further validates the input data (checking against spam). 
  Challenge: would like to retain form data in case of error in enterred capthca code and needing to return to form.
  If I use a sticky form with  the form sticks okay but I cannot see how I then direct http to the php script for form data validation.
  So I figure the answer is a javascript function to validate the captcha and stay within the same page where the form appears, ideally just having a pop up message (alert ...) if the enterred code is wrong, before sending the http to the php script page.<br>
  I have seen that this can be done but I cannot adapt the code to the captcha I use (i.e. webspamprotect.com) Could any body suggest a generic js function useable with any captcha ?
  Would be most grateful for any input.
  MANY THANKS
  Steve</p>