This list was produced by scanning over a million kanji on thousands of Japanese web pages and ranking them according to the number of times they were seen. In total, over 3200 distinct characters were encountered. However, in order to eliminate anomalous entries at the lower end of the frequency scale, the list was arbitrarily truncated at 2000 entries.
Each kanji character on this page is linked to its entry in WWWJDIC, an online Japanese dictionary that provides more information about the character and words that use it.
The list was created by a guy who's just one of many brains online (it's hard to meet such people offline). Think about it: he created a program to scan the internet to find frequently-occuring kanji. That's a lot of work! Plus, all you have to do is click a kanji to find out its info--ie, convenient programming. The only complaint I have is the font he chose--it's not the "typical" font you see in Japanese text. It looks more like Chinese, though it's not.