So IE6 is as old as the hills and should just go away, however the fact is that some people still have an use IE6 unknowingly. As a result its a good idea to make sure websites at least work and are readable in IE6. I also find that if youcode the xhtml and css to show correctly in IE6, it will look ok in all other browsers.
Anyways, Microsoft have a download which will let you preview a website in IE6. Its called “Microsoft Expression Web 3 SuperPreview”. Its a free download (see here), and be sure not to mistake it with the full Microsoft Expression package.
As for people who try and code for IE6, you get used to the quirks and know which css properties will fail and which will work ok. Typically css positioning will fail. Its best to use floats as much as possible. I’ve also found that IE7 has some quirks also. As a result its a good idea to test using the MS Expression SuperPreview. Also is possible to use compatibility mode in IE8 which will render websites as they would appear in IE7.