Let me start off by saying Internet Explorer for Windows is a pain in the butt. Why you ask? Where do I start? No built in pop up blocker. No tabbed browsing. No support for favicons. No PNG support (at least not fully). And worst of all, weak standards adoption. When I code my website, I test to see if it renders correctly in the different browsers that I have. I run it through Mozilla 1.3, Firebird 0.6, Internet Explorer 5.2, and Safari 1.0 on my Mac, and through Mozilla 1.3, Firebird 0.6, and Internet Explorer 6 on my PC. Almost every other browser out there has decent to good W3C standards compliance. When I run my code through these browsers, almost all of them correctly render the HTML code in my site. All of them except Internet Explorer for Windows.
For example, if you compare the way my site looks in Internet Explorer for Windows and virtually any other modern browser on any platform, it just doesn't render correctly. Call me a crappy coder but I think it's more the browser's fault than mine. That's just my opinion.
If you notice the two screenshots, one from IE for Windows (top) and IE for Macs(bottom), there are tiny white gaps between the banner and the navigation bar, whereas on the Mac browser, it renders correctly. "How can this be?" you say. "They're both Internet Explorer?" Yeah, they are, but IE for Windows just doesn't render code correctly.
I know what you're thinking. "How come I don't run into these types of problems when I surf the web?" Since over 95% of the online world uses some form of Internet Explorer on Windows, most web designers are forced to cater to the majority.