I experienced in the apache webserver logfiles executing JS "window.open('test.pdf')" does produce two HTTP requests in the logfiles (first load). Still, although loaded from the browsers cache the second time, this creates another entry. As for using "window.open('test.html')" this behaves as expected. I have been told - but not tested myself - this also applies for Safari 3.x. As for people runinng logfile analyzers this is a pretty critical beahavior as the statistics of downloaded binary files are not properly reported.
Created attachment 31167 [details] test scenario loading PDF & HTML files using window.open - creates two HTTP requests on server upon first load for PDF, beaves as expected for HTML file