camioneur: When rojash said that avast (and the others too) are just skins for IE, what he meant was that they use the same engine that IE uses to render and interface with websites. For this reason, Avast is no more secure than IE, and that means that it isn't that secure at all.
And yes of course, you're right. End users shouldn't have to care at all about what code has been used to create the website. However, it just bugs us that they're too lazy to write code that works everywhere, and no just in IE.
Note that this isn't an IE vs. firefox thing. It's a IE vs. everything else thing. Suppose a site only works properly in IE. You seem to think this doesn't matter and people should just stop complaining and use IE. However, not everyone uses IE. Hell, many people don't use Windows at all. IE wasn't the first browser, and for a good few years of the web Microsoft had no interest in it. It was only when they reaslised there was a lot of money in it that they did a 180 and made IE and msn etc.