I teach a Multimedia class at Plymouth State University. This week we were discussing the pros and cons on the use of PNGs. I mentioned that Internet Explorer versions 6 and lower fail to render the transparency of a PNG properly, placing white background in the transparency’s place. I also took the time to plug Firefox, mentioning that Firefox does it right!
Why only versions 5.5 & 6? Because Windows IE versions prior to 5.5 do not support the filter which fixes the PNG problem, and version 7 (not yet released at the time of writing in January 2006) is reported to have fixed the issue entirely.
The code can be used either by a one-time copy-and-paste or as an include file. The entire thing is completely ignored by all other browsers – in fact it is treated as an HTML comment – thanks to IE’s conditional comments. This solution is therefore light, portable and non-invasive to other browsers.