My site is flooded with abusive bots that spam my link exchange submit form every five minutes. I finally removed the form, and now they're spamming my main contact form every five minutes instead.

I created a thread before on how to block bots by IP, followed the instructions for editing my .htaccess file, but it didn't block them (the bots keep on coming). I'm using submit forms generated in Frontpage (as I have for years) and host this particular site on godaddy's servers. Is there a way for me to set an option so that a human user must manually toggle an option for the form results to be submitted? Or is there another type of submit form I can use on an html page that requires people to type in a graphic-based password that I have on the page?