At CFUN a few weeks back, I gave a presentation (with a bad name - Security) that talked about Bulletproof Websites. This is just a fancy way of describing a web site that cannot, and will not, break if input parameters (url variables, form fields, cookies) are messed with. How many web sites out there break if you change a simple ?id=5 in the URL to ?id=ray? Way too many.
By the way, I know my sites aren't perfect either. But it seems like people are not even coming close to considering error trapping in their application design. If this is a topic that interests people, I'll blog more on it later. Right now I have to eat or I'll waste away into nothingness. (Well, I'm probably a few dingdongs away from that. ;)