For those who have issues with png transparency - I've found this solution.
With the help of jQuery it adds some JS code for solving this issue.
Just add one one file and call one method on page load and here's the magic :)
http://jquery.khurshid.com/ifixpng.php

another two ways of solving the same issue:
http://homepage.ntlworld.com/bobosola/pngtest.htm
http://24ways.org/2007/supersleight-transparent-png-in-ie6