I found http://espn.go.com/browserupgrade_long.html#longanswer today. It does a pretty good job of explaining the concepts behind web standards.
We’d like to make perfectly clear that we are not trying to get you to use Microsoft browsers, Netscape browsers, Apple browsers, or Opera browsers. This is not about telling you what brand of browser to use. It is only about alerting you to the fact that each of the companies above, plus a few more, makes a modern, standards-compliant browser which you can easily (and freely) switch to using the links on the upper left side of this page.
I’m in that same boat as far as coding and stuff. I don’t care what you use, so long as it’s something that supports modern standards. I personally like Firefox, as I’m sure you’ve noticed by now. I could also call them on the standards support in Microsoft’s browser, but the main stuff is mostly right, enough that a modern version of IE should make the page look presentable at least. As sites start to use the newer standard code (just like the link says), I think people will see for themselves the shortcomings in IE and other browsers. Either they’ll complain enough to get the browser fixed, or they’ll switch to another browser that doesn’t have that problem.
Anyway, just thought this was a good explanation for non-techies…