PNG articles

Gradient Effect
32-bit PNG degradability in IE
Kevin A. Freitas, Web Developer (seattle php design web development consulting flash html css xhtml)

Now you need to save your graphic with just the right options to achieve the effect we're going for. Use the Export Preview option in the File menu. Set the Format to PNG 8 and choose Alpha Transparency from the pull-down toward the bottom. Adjust your color settings any way you like to get the best looking palletized image for your money. Notice that the palette for my image (at right) includes some colors with a little checkerboard over them. This represents colors that have at least some transparency to them and that won't show up in IE.

Windows Live Gadget Blog : Use GIF over PNG in your Gadgets

We have recently released a workaround for a bug in IE6 where image filters for PNG can cause a hang on the Live.com site. This IE bug is already fixed in IE7, but we still needed to workaround it to make sure the site works properly for IE6.
To understand the problem, here is an explanation from the IE team (thanks Peter Gurevich!):

* Each IE 6 window is a UI thread.
* The HTML page and any script you wrote for the page run in the UI thread. Therefore filters in your page or in script will download on the UI thread
* IE’s implementation of the AlphaImageLoader filter downloads images synchronously
* Synchronous loading of an image or successive images on the UI thread has the potential to hang the browser and adversely affect the user experience.