Looks like Google has broken their links.

You could maybe change it to this instead:
Code:
http://code.jquery.com/ui/1.10.2/themes/smoothness/jquery-ui.css
But that'll probably give you SSL/security warning errors if you're running your admin in SSL.

Another option is to copy the actual file to your own server and use it from there by entering the correct path for where you've put it.