We have plenty of evidence to suggest that a browser monoculture is coming back, a repeat of the monoculture that we as developers created when we built for IE6 only, and now we rail against as if it's the user's fault.

Not so long ago, IE6 was the over-dominant browser on the Web. Technically, the Web was full of works-only-in-IE6 web sites and the other browsers, the users were crying. IE6 is dead, this time is gone, and all browsers vendors including Microsoft itself rejoice. Gone? Not entirely... IE6 is gone, the problem is back. [...] I am asking all the Web Authors community to stop designing web sites for WebKit only, in particular when adding support for other browsers is only a matter of adding a few extra prefixed CSS properties.

In rare situations it may be necessary to provide different rules, not only to the Internet Explorer family in general, but also to each individual version. We can combine 3 CSS Hacks to achieve this.

But beyond selectors not being implemented, there are two BUGS when it comes to selectors in IE6:
The multiple class bug
The ID-class bug

Are you forced to use an outdated, buggy and insecure browser at work? Corporate I.T. policies are slowing the pace of web tech progress. And yet the reasons to upgrade are well documented. IE6 Offenders is here to give you a voice.

In our article, ‘Calling time on IE6’, we ask designers and developers if it’s finally time to take IE6 behind the shed and shoot it. Major names in the web industry debate our mission, talking about the pros and cons behind dumping IE6. How feasible is it to shun the browser entirely? What can you do to minimise the impact IE6 has on you and your clients (and increasingly tight budgets)? And what can and should Microsoft do to help us all move the web and web standards on?

However, our client had one last, heart-stopping requirement: the design had to be fluid and resize with the browser window.

This is a Javascript library that sandwiches PNG image support into IE6 without much fuss.

AlphaImageLoader filter flaws in IE6