My friends! How can I secure my guestbook and forum from posts such as:

<a href=http://www.quizilla.com/poems/8835643/buy-anti-asthma-m edication>buy anti asthma medication</a>,<a href=http://www.quizilla.com/poems/8835585/buy-muscle-relaxe rs-online>buy muscle relaxers online</a>, <a href=http://www.quizilla.com/poems/8835613/buy-erectile-dysf untion-pills-online>buy erectile dysfuntion pills online</a>, <a href=http://www.quizilla.com/poems/8835666/buy-body-building -supplements>buy body building supplements</a> etc...
I am tired from it!