To fix PNG transparency in Windows Internet Explorer 5.5 and 6, Danland 6.x use jQuery pngFix by Andreas Eberhard, for the 7.x version of the Danland theme, I get rid of this jQuery plugin.
And for those of you who want to add jQuery pngFix into Danland 7.x, you can follow the steps I've made here. I just improving the existing codes in Danland's template.php.
Note: remember to clearing the Drupal cache after you've done with it.