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Showing posts from February 28, 2010

Advantages Of FeedBurner And Some Web Feed History

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Perm url with updates: http://xahlee.org/js/feedburner.htmlAdvantages Of FeedBurner And Some Web Feed HistoryXah Lee, 2010-03-06Today, i have to make a decision on whether to use the FeedBurner free service for managing my web feeds.Advantages Of FeedBurnerAdvantagesProvides statistics. For example, how many subscribers you have.Possible to monetize. You can have ads on your feed. Without some type of feed service, adding ad to a web feed is quite difficult.Provides better feed interface. For example, users can click on a link to add your feed directly to their feed readers, such as Google Reader. Also, feeds pages (RSS/Atom) often cannot read by browser directly. FeedBurner turns your feed into html so can be read by those who are not tech savvy.DisadvantagesYou lose total control of your feed. There are several aspects.Your domain name is no longer in the feed url. For example, your feed address may be like this: http://xahlee.org/js/blog.xml. When using FeedBurner, your feed url i…

Bird Flight V Formation As Geometry Problem Of Max Visual Contact

perm url with updates: http://xahlee.org/math/bird_flight_v_formation.htmlBird Flight V Formation As Geometry Problem Of Max Visual ContactXah Lee, 2010-03-05Was reading Wikipedia V formation, that is, the formation of flight of geese, ducks. The interesting thing is, why they fly in that formation. The Wikipedia article is quite interesting, but too short.The reason given by Wikipedia are basically two: (1) for the whole group, the V formation is more efficient for (energy cost)/(distance traveled), and increases flight distance up to 71%. (2) Visual contact is part of the reason for V formation.It is interesting to note that the birds in V Formation rotates. The bird in front is the most tiring. Though, Wikipedia doesn't say how often they rotate, or how they rotate, or by what biological behavior means the signal a rotation, i.e. instinctively by bio-clock?I thought a bit about the visual contact reason. It is essentially a mathematical problem. Each bird has max visual contac…

Why Emacs is still so useful today

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Perm url with updates: http://xahlee.org/emacs/emacs_power_story.htmlWhy Emacs is Still so Useful TodayXah Lee, 2010-03-04This essay tells a little anecdote about why emacs is still essential and superior among today's tools.ProblemToday, i need to rework some of the markup in a html page Wallpaper groups: References and Related Web Sites. The page is a bibliography. Each entry had markup like this: <divclass="entry"> <spanclass="w">Title</span>: <b>Regular Polytopes</b> <spanclass="w">Author</span>: H.S.M. Coxeter<br> <spanclass="w">Publisher</span>: Dover<br> <spanclass="w">Date</span>: 1973.<br> <b>Notes:</b> 3rd ed.<br> <spanclass="w">Subject</span>: Symmetry<br> <spanclass="w">Comment</span>: A standard reference...<br> </div> This page was written in 1997, and the…

Flowing List Items

Perm url with updates: http://xahlee.org/js/css_flow_list.html(css effect may not show in blogger. Visit the link above to see full effect.)Flowing List ItemsXah Lee, 2010-03-03This page is a html/css tutorial, showing you how to format list items.By default, list items are formated like this:CatDogBirdHere's the code: <ul> <li>Cat</li> <li>Dog</li> <li>Bird</li> </ul> This is plain. Sometimes you have a list of items, but you want them displayed in different format.Flowing List ItemsFor example, if you want it to flow like this:CatDogBirdHere's how you do it: <styletype="text/css"> li.mystyle { float:left; list-style-type:none; border:solid thin red; margin:1ex;} li.mystyle:before {content:"♥ "} </style> <ul> <liclass="mystyle">Cat</li> <liclass="mystyle">Dog</li> <liclass="mystyle">Bird</li> </ul> <hrstyle="…