An online service providing system, a method, a server, and a mobile device thereof, and a computer program product are provided. The method includes sending a verification link corresponding to a user account that is not verified; after receiving a verification request corresponding to the verification link, determining whether a device identification sent by the mobile device that has logged in the user account is received; when receiving the device identification, confirming whether the user account is verified according to the device identification; after confirming that the user account is verified, when receiving a service request sent by a terminal device logging the user account into a service website, determining a homepage of the service website according to the device identification, and providing the online service corresponding to the mobile device to the terminal device through the service website.