What is the best web browser - Firefox, Opera or IE6?

You don't specify version numbers for Firefox or Opera but I will assume you mean the latest version so 1.5 and 8.5 respectively. Assuming this Opera is the best browser. Opera provides a very clean interface and a whole range of features, and it is the fastest browser that I have ever used. However despite it's feature-rich style Opera is not bloated, and its download size and loading time are significantly less than Firefox. Firefox 1.5 improves on the features of previous versions with better tab controls. It is still not as good as Opera though. IE6 is somewhat in the past. Current information about IE7 suggests that it too will lag behind the competition.