At first, you incorrectly use
StringBuilder
. This class was created to avoid recreating string objects in heap. So instead of "+" you should use Append method. But actually I recommend you to use String.Format here, here is example:
String.Format("http://maps.googleapis.com/maps/api/staticmap?center={0},{1},{2},{3},{4}&zoom=14&size=400x400&sensor=false", strProvince, strCity, strSuburb, strStreetName, strStreetNo)
Regarding error, it is what it says. So if site is unavailable via your url this means that site is unavailable. Compare originally created URL with yours.