Custom Font - what to enter

Hi there,

I am using a template (Cepon - nope, no support from them!) that allows "Custom Font" in ThemeMagic, but I have not clue what string to put into it. I tried any combination available from Google Webfonts (e.g. http://fonts.googleapis.com/css?family=Droid+Sans:400,700 or just family=Droid+Sans:400,700) but it all results in an error (see screen attached).

Any idea what exactly I have to enter?

Many Thanks
C.