Google will let companies use competitors' trade marks as keywords to trigger search adverts in all European countries for the first time. The move will test the interpretation of a number of EU and national court rulings on the controversial practice. Google's AdWords system sells the right to have an ad displayed when a specific term is searched for in the Google search engine. The adverts are displayed beside the natural search results, ranked by which advertiser bid most and by the ad's relevance. Many of the keywords sponsored by companies will be general words, such as 'car', or their own brand names. But some advertisers use competitors' brands as triggers for their own ads. Some companies claim that this practice is an infringement of the competitor company's trade mark rights, and courts in France have ruled that the practice infringes trade mark rights.The European Court of Justice (ECJ), though, ruled that a trade mark right is only infringed if the advert creates confusion about what company is behind the advert.