I have lot's of icons that are PNG's, just like your TUX's. How do I use a PNG to make it look as glamerous on a site or elsewhere. If I use it as PNG, the edges go ugly. Am I doing something wrong?

PNG save the Alpha-Channel of an image...
If you use it on a site, be careful at the premultiplied color. (the color witch replace the transparency)
Perhaps have you to tweak this parameter ?

Excuse-me for my bad english  

No problem, thank you for answering but what do you mean by tweaking the parameter?

I open it in Photoshop and then do what?

Example: my avatar looks great here, how was this saved and done?

I'm not a web developper sorry
I have only wanted explain to you, why you've got alising on the edges !
In After Effects for example, when you import images with premultiplied alpha, it will prompt you to "ignore, select premultiplied color, or disable..."

I think your soft disable this "alpha conservation" fonction...

Are you using Internet Explorer?

if yes, you should look at this web site:
PNG in Windows IE

Hmmm, I installed the .js script but it didn't help

Will try again later, thx for your help

The gif format save Alpha. Perhaps can you have less problems...