QWhat is the meaning of the numbers and letters in the lower left corner of each page?

The numbers are the date (as and time (as hour:minute:second) of last modification of the page (or of the PHP script that generated it), followed by the time spent on the server for compiling the page (as seconds:centiseconds). The 'v' links to a W3C validation service that tests the (non-AJAX generated part of the) code of the page against HTML Strict 4.01. The 'i' links to a page containing technical information for the site as a whole.