Internet Explorer: The Absolute FAIL.
The first day I started programming websites, I noticed that Internet Explorer always gave more trouble than Firefox due to its non-compliance with the standards set by professionals. Microsoft's employees probably were drunk when they decided to make only "padding" or "margin" work in certain situations. Firefox is much more lenient, and allows for better code organization. Opera is the best at this time for obeying standards, although it is not as open to small mistakes as Firefox is. I appreciate the need to obey the standards with Opera, because it forces me and others to learn what our mistakes were and fix them.
The other day I noticed that my "IE Hacks" for a site were making Firefox display a website in a weird fashion. I ended up spending 3 hours just trying to align an image correctly, making padding and margin (two different ways to space things in CSS styles) fight against each other in a bitter battle of pixels. I was frustrated to no end, because in reality I should not be using padding, the only spacing that worked at that point for IE, I should be utilizing margin, which makes much more sense.
Internet Explorer has been around so long, you'd thing that they would obey standards. Why not? They ARE the most popular browser by far... Microsoft's highly successful product just doesn't cut it compared to the others. According to various sources, Internet Explorer 8 will be really high quality and obey the standards of programming much better. I will wait and see.