It was very common back before Firefox. Netscape, Opera and Omniweb (which in Mac OS X's early days was the best browser for that platform) were the biggest one

It was very common back before Firefox. Netscape, Opera and Omniweb (which in Mac OS X's early days was the best browser for that platform) were the biggest ones. Internet Explorer made it a very tough sell on Windows, and Firefox and later Chrome completely destroyed the market by giving away a better browser than the commercial ones or Explorer. Opera and Omniweb ended up going free as well because the market just wasn't there anymore.