Download a file through AppleScript

I've been trying several different methods to download a file through Applescript. I've looked at different sites/discussions and I've tried to use curl, wget, and some other ways, however I still can't get it to download the file. It'll either just not download, or no URL specified.

Here's what I have for the curl shell script I was using:

set alertquestion to display alert "Bukkit Server folder has been created" message "The folder was placed on your desktop. 'Craftbukkit.jar' will now be downloaded to that folder. Continue?" buttons {"No", "Yes"}

set alertanswer to button returned of alertquestion

if alertanswer is equal to "Yes" then

do shell script "curl -O http://cbukk.it/craftbukkit.jar"

end if