Hey Natzy24
IE7 added PNG support so that problem is atleast partially corrected.
However, the bain of every web developer is IE6... still the most common browser in use and the least predicatble of all...
IE6 does still ignore PNG Alpha transparency, resulting in the teal/blue on transparent PNG images.
There are a number of javascript methods to resolve the issue that allows you to use them even in IE6, but it's at best an archaic way of fixing something that should never have been broken in the first place...
The CSS Behaviours hack:
IE PNG Fix - TwinHelix
The AlphaImageLoader method:
PNG in Windows IE
or
PNG-24 Alpha Transparency With Microsoft Internet Explorer 5.5 or better (MSIE 5.5+)
Fix for Backgrounds:
Remote Synthesis: IE PNG Fix with Background Support
Hope this helps someone!
Cheers.