When a company uses or impersonates the trademark of another company, resulting in confusion or deception of consumers. Trademark infringements are commonplace online. For instance, the use of keywords based on a competitor's brand name for search engine optimisation or pay per click advertising, with no mention of the competitor brand in the advert. Basically, trying to take advantage of the brand strength developed by the competitor for promotion of ones own site. Or when the trademark is included in the text of a competitor's advert. Both infringement are a good case for the search engine company to act on behalf of the trademark holder.

A trademark registration is infringed by the unauthorized use of the registered trademark, or of one that is confusingly similar to it, on the registered goods or services, or in certain circumstances on similar or dissimilar goods and services.

The use of any portion of another company’s advertising campaign or trademark to sell third party products.