IE6 has to go. IE7 is looking good but it still sux. Conclusion is, IE sux. Sadly, there's an IE on every Windows machine (including mobile).
The main (modified) theme of my forum does not look the same in IE6 as in Firefox and IE7. Can't believe the nested divs trick (outer div has fixed width and zero padding while inner one has non-zero padding) doesn't work in IE6 since the inner div insists on inheriting the outer div's fixed width and increase it by the padding value. I just don't bother to fix it.