Not long ago, online advertising was considered a turn-off and in decline.
Google's adverts, however, manage to strike the right balance between useful and unobtrusive.
Search on Google for "France holiday hotels" and your results page will be surrounded by "sponsored links", little adverts that just happen to be exactly what you are looking for.
Click on one of them and the Google cash register rings, to the tune of about 50 US cents a click say analysts, although some keywords are much more expensive.