A device (1) for indicating downloading of a data item (3) by a user computer (5) from a first computer (7) using a data communication network (9) is disclosed. The device (1) comprises a processor (13) being configured for receiving an upload instruction for uploading the data item (3) from a second computer (15) to the user computer (5) via the data communication network (9). The upload instruction has been generated by a first markup language tag referring to the data item (3). The first markup language tag has been generated by a browser executable script uploaded to the user computer (5) from the first computer (7). The first markup language tag differs from a second markup language tag in a cache memory of the user computer (5) causing the user computer (5) to download from the second computer (15). The first and second markup language tags were generated by the browser executable script. The processor is also configured for indicating that the upload instruction has been received. Also disclosed is a device (1) for calculating an estimate of a number of downloadings of a data item (3) from a first computer (7) by a first group of user computers (5) which are configured for not allowing execution of a browser script and the cache memories of which comprise the data item (3).