Chilimagik

Well recently I have been getting loads of emails sent through my contact form on my site which is just a basic script.. how can i stop this? I know about using images etc but dont know where to start..

Ok Im writing a tut managing system.. so I want to wrap all code in bbcode tags e.g. [code] [/code] to do this ive used preg_replace which works but as soon as I use "'s or 's in the [code][/code] tags it dosent work.. any ideas?