How many browsers to support?

[Gruntled]

Stats for the site will show which browsers are in use and by what percentage of visitors.

Netscape and MSIE are the only ones that really pushed anything outside of w3c standard html/dhtml/css. So when you have requirements like that, the main concern is designing the site for the lowest screen resolution and for the oldest browser. Once that is done, check for standards-compliance in your code, then check with each browser.

There has never been time that I needed to sniff for the browser, then throw exception html in the case of Opera, Safari, or Mozilla.