Hi *!
I have for my website a form to sign-up for some service. Now, in order to disable automated sign-up I want to display some image (that displays some text) and the user types-in that text manually to be able to sign-up successfully. I am not sure what it is called , tried googling for "disable sign-up image" and some variants of it, but the results were not too much of help.

I am using php5 on my website.

Any comments/suggestions are highly appreciated,

Thanks in Advance,