The contact form on this site uses a 'CAPTCHA' system to help prevent if from being exploited by bots or spiders.
CAPTCHA stands for Completely Automated Public Turing Test to Tell Computers and Humans Apart. It requires you to enter a code that appears in an image. This means you need to be able to read the letters and numbers and recognise them, which is something computers find hard to do (currently - they're getting better), but humans are very good at (I doubt that'll change much).
There are several motivations behind people writing bots, a great number of them are useful and operate ethically. For example, search engines use bots to follow links on the internet in order to produce their indexes. However, other bots are used to trawl the web looking for email addresses that can then be spammed, and others look for contact forms that they can then attempt to exploit to send spam.
It's attacks like these that the CAPTCHA system is designed to prevent. No CAPTCHA is completely unbeatable, but the harder it is to exploit a form, the less likely it is that someone will attempt and succeed.
If you encounter any problems with the form, please let me know at .