I remember the old days when Netscape aka Mosaic was around and took 90% in the mid-90’s. Then others came in and they lost valuable time by rewriting the whole thing. By 2006 it fell under 1%. (Read more @ wikipedia). I loved Netscape because it came with a simple editing tool for free, a feature none of todays browser packages offer anymore (per default).
Today we have IE (no. 1), FF (no. 2), Opera, Safari and some other browser.
Since August 2007 Microsoft is working on IE8 and they just release last week the second beta version for public download and evaluation. I propose doing that in a virtual machine. (link)