Various background images for each week day
From ISO 8601: “… [D] is the weekday number, from 1 through 7, beginning with Monday and ending with Sunday. This form is popular in the manufacturing industries. …” So I wrote small php css switcher which is loading different backgrounds images each week day on all pages (excluding library e-texts) according to ISO from 1 to 7. All index-pages (the main section pages as linked everywhere in the page footer) have their own theme: Deoxyribonucleic acid but daily changing for them is only temporary (probably). All background images are as following.
Background images from Tuesday to Saturday, I've downloaded from Vectorilla.com (Collection of web designs stuff). As always, only free programs used: PHP <http://www.php.net/> and CSS3 <http://www.w3.org/Style/CSS/>
Original images are also here. First index pages (DNA themes):