The nice thing with Explorer that there are many asshole webadmins making IE only sites. The problem lies in that there are a thousand IE variants, sometimes even under the same version number - using the same version numbered english, french, hungarian browser behaves differently. Not to mention the differences between the Win and Mac Internet Explorer. Not to mention that IE has some hair raising design faults, so you will have a tremendous list of things to avoid if you want your code/html to display/run well in IE.
Internet Explorer is a nightmare.
