The short answer:  all of them.

According to NetMarketShare, Internet Explorer still has, what is considered in politics, a 62.18% complete landslide domination of the other browsers.

So we can read:  62% IE, and 38% “not IE”.  But that doesn’t work in practice because the other 38% is fragmented among at least 4 other major players (major being defined as more than 1% market share, or about 17,300,000 installations).  Think about it.  Opera has over 41 MILLION users.  So that 2.38% is still not anything to sneeze at. . . unless you are serving the 1,075,714,000 IE users.  Wow.  over 1 billion Internet Explorer users.  (Internet stats from “Internet World Stats”)

At Headspring, most of the current market wants a mix of web, windows, and mobile business applications with a heavy, heavy lean towards web applications.  As a Microsoft shop, ASP.NET is dominating the line-of-business space for us.  We have to decide which browsers to support (which really means which browsers to heavily test).  Yes, the client might have some browser preferences, but most of our clients trust us to do the right thing for them.  So what do we do, and what browser do “I” run?  See above (I run them all).

First, we have to look at the base of users and what browser they are typically running.  A really popular combination is IE 7 and Firefox 2.  Yep.  Version numbers.  We have successfully deprecated IE 6 support down to the functional level (must work in IE 6, but visual discrepancies won’t be fixed) because clients have either migrated or they plan to migrate within a year, and we present the cost/benefit of the alternatives.  Any clients needing Chrome support?  Nope.  none.  not even a mention.  Now, in our experience, if a web application works properly in IE 7 AND Firefox 2, it is highly likely to be just fine in the other browsers.

Now for me.  Yes, I run all the browsers, but I have chosen one for my day-to-day browsing needs.  That browser is Google Chrome 4.  Not Chrome 3 or 2.  But 4.  And it’s only today.  Why?  Because I think Microsoft is going to wake up and deliver a really killer Internet Explorer that will push it’s market share back to 90% in the coming years.

Let me back up:  for running software applications, it is critical to use the browser that the client will be using (and if it requires a different version of IE, then just run it from Windows 7 XP Mode).  If your client is predominantly Firefox (like some timid IT departments now), then you must test your app predominantly in Firefox.  Same for IE.  Ignoring the dominant browser at your client is a really good recipe for obvious bugs to slip through.

Now, why Google Chrome 4?  Because of the architecture of the browser coupled with new support for extensions.  Each tab runs in its own process.  This is critical because it delegate memory isolation and threading to the operation system instead of trying to manage them all within a single browser process.  Next is extensions.  First, and my favorite, is the IE Tab extension, ported from IE Tab as a Firefox extension.  It runs the page in the IE rendering engine but inside a Chrome tab (which is isolated to one process).  Note that this cannot fully replace actually TESTING with IE proper for your clients.

Below is an image of two Chrome tabs.  The top is regular, and the bottom is with IE Tab.

My next favorite extension is just named “Keyboard Navigation”.  It’s just like the really great Numbered Links Firefox extension that makes it possible to really browse the web without the mouse.  You press the comma(,) hotkey to pop up the shortcuts, then choose your link.  The enter key directs your browser to follow the link.  All while keeping your fingers on the home row.

I don’t use IE and Firefox anymore for my normal browsing for one single reason:  The process architecture.  Having all the tabs in a single process produces a slow browsing experience (when contrasted with the alternative).  Does Chrome slurp up more memory?  Absolutely.  Here is a screen shot of all the processes.

A quick glance produces over 500MB or RAM used just for the browser.  If I was worried about RAM (and willing to spend my time waiting in order to save RAM) I would probably make another decision.  But, when all my guys are equipped with 8GB of RAM in the company computers, it’s just not a constraint to worry about.

I’m not an Internet Explorer MVP, so I don’t get early access to IE information and roadmap plans, but I do expect a big breakthrough on that front to be announced in 2010.  I think the sleeping browser giant is about to wake up.