Creating a guestbook
The next task up the difficulty food chain is creating a guestbook - a textual log of messages from visitors to your site. Programmatically speaking, guestbooks are actually easier than polls to write because you need only store a chunk of user text directly in your database. The reason I have covered polls first is because guestbooks are inherently insecure - when you just allow users to click a button to select their entry there is little scope for error, but when you take their input and need to use that for text entry into your database, you become a much juicier target.
Guestbooks are usually most common on personal homepages of any size, but are generally not appropriate for corporate sites as you may get abusive users posting there. Do not believe me? Consider this: I once created a Prayer Board for a local church, which was effectively a guestbook, and even that had a number of abusive messages posted there by people who clearly have a lot of time on your hands.
We'll be looking at this and other security concerns related to guestbooks here.