Use the Drupal CAPTCHA module to avoid spam on your website

A CAPTCHA is a challenge-response test most often placed within web forms to determine whether the user is human. The purpose of CAPTCHA is to block form submissions by spambots, which are automated scripts that post spam content everywhere they can. The CAPTCHA module provides this feature to virtually any user facing web form on a Drupal site.

Theming contact form:

#contact-site-form fieldset {

border: none;

}

#contact-site-form span.fieldset-legend {

display: none;

}