validateMessage

function validateMessage(){
    var notAllowed = ['viagra','ciallis','penis'];

    for(var i = 0; i < notAllowed.length; i++){
        if(document.contact_form.cf_message.value.indexOf(notAllowed[i]) != -1){
            alert('The word "' + notAllowed[i] + '" is not allowed');
            document.contact_form.cf_message.value = document.contact_form.cf_message.value.substr(0, document.contact_form.cf_message.value.indexOf(notAllowed[i]));
            break;
        }
    }

}