But IE stylesheets can only get you so far. When working with a public-facing website design you just need to get it right once: we make sure the structure is flexible and adaptable and forward-looking, but mainly we build to the best standards of the current day. But because development of our backend solution will be continuous (that’s a hint about a major feature, by the way), continuing to tie ourselves to IE6’s sundry limitations would be crippling down the road.

All this is to say that we’ve made a careful and tentative decision to drop IE6 support for the backend web app. The software is seven years old and was buggy when it was released; its replacement is already two years old. Still, requiring a more modern browser felt somewhat risky: about 20% of visitors to the public pages of a small liberal arts college are still on IE6; at a major research university, the portion is slightly higher. But we decided that a fully-fledged rich “web application” can have different requirements than a public site, and now we see that we’re in good company: both Apple in MobileMe) and 37signals (in all their apps) have decided to drop support for IE6. Hopefully this will be the start of a sorely-needed chain-reaction–it’s clear that the catalyst is not going to come from Microsoft, which is not at all interested in pushing the upgrade, even with version 8 on the horizon.

So if you’re using IE6, might we suggest an upgrade to Firefox, Safari, or IE7? Your web experience will be leagues better. And you’ll be able to play with our new toy as soon as we release it, just around the corner.

Getting these PNGs to actually be transparent is no longer a major issue—we’ve used a few different approaches over the years, but settled on Angus Turnbull’s iepngfix.htc as the most straightforward drop-in solution out there. The way it works is just really smart.

But while building out some recent client projects, we just couldn’t get it to catch. We checked and double-checked the file paths, and re-exported the PNG images, and finally copied a working example from a live client site, but nothing seemed to do it. Because IE has no decent debugger, I removed the conditional comment to see what I could learn in Firebug.

It turns out that our staging server sends the .htc file as text/plain, while the working client version was serving text/x-component. Changing out server config to mimic this fixed the problem. Later, some Googling revealed that the release notes for the newest beta version address this (and even include a PHP solution that serves the file while sending the correct headers).

There are still a whole host of limitations: no repeating images, weird layering glitches that happen even in IE7, and really bizarre link clickability issues. But iepngfix gets far enough to solve 90% of the problem.