A thread at WebmasterWorld discusses how every time you click from a search result in Google, the result opens in a new window. The member describes the code being used as;
Google inserts this piece of code: ---------------------//--------------------------- <script><!-- if (window.name == 'nw') { window.name = '';} //--> </script> ... <a href="http://www.foo.com/" target="nw"><b>Foo</b> ---------------------//------------------------
You do know that Google has an option to "Open search results in a new browser window" in the Google Preferences page.