If and when you want to know what the current browser usage statistics are, here are some relevant links:

• http://news.com.com/Study+Firefox+still+gaining+on+Internet+Explorer/2100-1032_3-5435176.html?tag=nl
• http://statmarket.com/html/sample_browsers.html
• http://websnapshot.mycomputer.com/

Here are statistics on what browsers people used to access Google, from http://www.google.com/press/zeitgeist/zeitgeist-jun04.html

The latest data is from June 2004

And I recommend you read this site before you trust in usage statistics:

http://www.dantobias.com/webtips/brand-x.html