In the Opera directory on the user's hard drive is a directory named ACPO . This is where Opera stores the metadata which tells where on the internet to find banners. There is one file in Opera's ACPO directory for each banner that has been loaded at the request of the ad-related service. When you click on a banner, Opera reads the ACPO file for that banner. Opera checks the ACPO file to find the banner-specified URL, and then Opera opens a new window on top and does a usual DNS lookup for the page which was advertised in the banner.
Some banners have a refresh tag, and refresh when there is network activity.
If a banner expires, and all it's data has been sent as part of the activity report , Opera deletes both the file from the ACPO directory and the relevant banner from the cache. New banners are also requested at a time specified by the content server. Also, clicks on the banners must be reported. The Service Transaction Provider Cydoor decides when it wants these activity reports and Opera stores this time information in the system registry as the number of seconds until the next time Opera should connect to the report server. An example is provided in no name yet .