The core activities of Yahoo, Altavista etc. are considered to be the Web search engines. This activity is classified in ISIC class 7240 (Database activities).
The decision to use this activity rather than advertising (even though advertising will generate a higher income) is in line with common practice in other industries as well. If advertising were given the priority, publishing of newspapers and all TV and radio programs would disappear and be lumped under advertising, which would not be of interest to most analysts.
There are also other activities that are now offered by companies such as Yahoo, that should be treated independently (if possible). An example for this would be the provision of Web access, i.e. the conpany acts as an ISP, which is classified in ISIC class 6420 (Telecommunications).
Explanatory note should be changed to reflect this.