JAB_Creations - 9:11 am on Mar 26, 2010 (gmt 0)
Already on page two and no mention of Gecko?
You can't discuss this topic without directly talking about rendering engines. You might as well have everyone suggest you test in IE and AOL even though both use Trident.
Gecko - Firefox, Camino, Netscape
KHTML - Konqueror
Presto - Opera
Trident - Internet Explorer, AOL, Maxathon
WebKit - Safari, Chrome
You don't need to test all possibly browsers, just the versions of rendering engines.
KHTML is so rare it's just not something most would consider. I mean if you care about the single digit percentage then sure, load up a KDE/Linux OS and test it out, there are some issues that you'll not appreciate and want to fix unless you're not doing anything fancy.
Gecko versions are pretty easy to figure out...
Gecko 1.7 = Firefox 1.0
Gecko 1.8 = Firefox 1.5/2.0
Gecko 1.9 = Firefox 3.0
Gecko 1.9.1 = Firefox 3.5
Gecko 1.9.2 = Firefox 3.6
Gecko 1.9.3 = Firefox 3.7...possibly to become Firefox 4.
Presto is used in Opera which simplifies that. Consider what your users are using and test with a version or two older, not that you'll have difficulty with that as Opera users are very good at upgrading.
WebKit is a fork of KHTML. You don't need to test both Safari and Chrome. Also Chrome's versions aren't like Safari's with major WebKit releases.
Safari's major releases have been (that you may want to support) 2.0, 3.0, 3.1, and 4.0; 3.2 was not a rendering engine update according to it's documentation.
That's how the engines and browsers correlate. Why this hasn't been discussed yet well...let's just say that's why Microsoft won't remove the Mozilla bit from the user agent.