I think text is the wrong approach. Put up some pictures, and a question - 'Click on the white bunny' 'Click on the chipmunk' 'Click on the Russian icon'. 'Click on the clowns nose' 'Click on the clown's right hand'

Taking text, which is explicitly designed to be readable, and trying to find a degree of distortion which is human (but not machine) readable is probably a bad approach. Try something a 6 year old can do, but which is still a PhD thesis problem for computers.

Actually, I thought about that option. There are two problems with it: First, I need to find a bunch of non-copyright clip art which displays clearly on any different browser, and then map it, and then write a big database of questions. This isn't difficult, but it's time-consuming. I'm a big believer in "do something now, refine it later on". The second problem with that is that for one of my applications, it needs to be highly cross-cultural. Many of the users will be non-English-speaking, who might not know what the word "clown" means, and any non-abstract image has a potential for offending someone. If one of my images is a pig, maybe some Orthodox Jews will be annoyed. If one image is a woman with her face exposed, maybe some Moslems will be offended. If one image is a policeman, maybe some c'punks will be offended. Who knows. People are constantly seeking new ways of being offended as a way of telling other people what to do. People should have thicker skins, but they don't, and when it comes to making money, I want customers, not controversy. The last thing I want is for some rumor that my system is anti-something because some image of something-or-other is used. As an example, for years there have been rumors about Proctor and Gamble being run by Satanists, because they have stars in their logo. Not goats, or a head with horns, but plain old stars! A hundred-year-old well-established brand! In my effort to support the largest user-base possible, numbers are the way to go. (Oh wait, maybe I had better put a filter so it doesn't display 666 or 69 or 444 or 13...) I'll make improvements as I go.