PNG's are by far the best format for transparent background images.
It's too bad IE5 and IE6 render them incorrectly. If you are using transparent PNG's on your website but when you view the site in IE6 the PNG is not transparent, with our PNG Fix the script will run throughout your website and on page load will fix all the PNGs in IE6.
The PNG fix we use is not powered by MooTools so you will not experience any script conflictions with Mootools.
PLEASE NOTE: Using JavaScript of any kind does not always guarantee a perfect fix for your PNGs in IE6. In some "very rare" cases when the page loads not all PNGs will be fixed properly or even show correctly, upon a browser refresh the results will usually fix the PNGs that did not show correctly.