Sorry, I don't understand?
Do you mean the Sample URL? Can by homepage of a site using that captcha or the captcha url itself.
you mean to download captchas in SDK?
You can try this...
1. in webpage use the url where the captcha is displayed.
2. in captcha url use just some part of the captcha url...not starting with http://...
this will tell the program to search for the captcha on the webpage.