Weekend coding: Add a character counter as the background of a textarea with JavaScript | CodeUtopia
http://codeutopia.net/blog/2009/08/01/weekend-coding-add-a-character-counter-as-the-background-of-a-textarea-with-javascript
"Have you ever filled a textarea on a page, which had a limit to how many characters you could type into it? ... How to effectively communicate how many characters you can type into a box, and have it look good. ... Add the number counter as the background of the textarea!"