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.
when one party uses the mark of another party in a way that creates a likelihood of confusion, mistake and/or deception with consumers.
Trademark infringement is a violation of the exclusive rights attaching to a registered trademark without the authorization of the trademark owner or any licensees (provided that such authorization was within the scope of the license). Infringement may occur when one party, the "infringer", uses a trademark which is identical or confusingly similar to a registered trademark owned by another party, in relation to products or services which are identical or similar to the products or services which the registration covers. An owner of a registered trademark may commence legal proceedings against a party which infringes its registration.