Depend where the server is located. In this case its UK law that dictate the rules. If it did go to court, I would suspect that the case Public Relations Consultants Association Limited [PRCA] v. The Newspaper Licensing Agency Limited and others (http://www.ip-watch.org/2013/05/07/viewing-cached-copyrighte...) would be relevant.

"The court said: Whether looking at a cached copy of protected content, without downloading or printing it, amounts to infringement. Lower courts held that it does, a finding unanimously rejected by the Supreme Court.".