No, the icons just indicate releases. They're at different vertical levels so they don't obscure each other. :-)

I decided to start in 2006 to catch Firefox 2 and Internet Explorer 7, otherwise you don't fully see the gaping hole which represents the Dark Ages of the modern web. (Safari was added later, and 2.0 happened to slot in at the start of 2006.)

I think it would be better to have every browser on it's own line. Especially with IE and Safari as their icons look quite the same from a distance.

Edit: My attempt at it. Not as pretty, but a bit more readable:

http://www.phoboslab.org/crap/modern-browsers-ship.png

Each set of browser icons are at the same vertical height. If it gets more complicated, I might move things around a bit.

In this pic you can really see that IE has HUGE gaps between releases.

It would be pretty cool if you extended it back to 2001, when IE6 was released - then you could also show the rise and fall of Mozilla and the birth of Firefox.

Even better, roll it back to 1991!

Edit: and another pony request - how about putting the release date in the tooltips (yyyy-mm-dd) to clarify any confusion about when exactly it was?

IE7/8 are there to show scale. The premise is that modern browsers release frequently. You can see that in the time it took IE to release 2 versions, the other browsers released at least double that same amount. Thus IE is not a modern browser.

The contrast I most hoped to illustrate was Chrome vs. everything else. :-)

I don't think the height means anything. As far as starting with Safari, they probably just picked 2006 as the start point and it was the first one with a release that year.

The reason it shows IE7 and IE8 is to illustrate that all of the modern browsers are shipping pretty regularly, while IE only has two releases on there.