Dismissing the alert makes the page reload in Firefox. Notice that the time of the page updates.
In Konqueror (KDE browser), dismissing the alert causes a directory listing (when file is local).

Reference: http://www.javascriptkit.com/javatutors/datedifference.shtml

• To examine the script code, use Ctrl+U which is the Firefox/Chrome way to see the page source.
• For Safari on the Macintosh, check these instructions: http://webdesign.about.com/od/safari/a/view-source-safari.htm
• "To view the HTML source code for a Web page using Internet Explorer 3.x and later, click Source on the View menu. To view the HTML source code for a Web page using Internet Explorer 2.x, right-click the Web page, and then click View Source." (http://support.microsoft.com/kb/176222