Hello,
I prefer to use PNG. However, if you're using transparencies and of the like, it will not work very well in IE6.

I hope this helps.

Hi SteveW,

Ryan hit it right on the head....

...png was not supported by MS at the beginning hence the message you're getting in front page.

Opera and Firefox do support png transparency as does the new IE7 when it reaches general release.

It was an evolving standard that MS didn't adopt earlier and now it's becoming a problem for web designers.

The side effect of using png in current IE incarnations is that you will see the edge of the pictures that you crop not blending in with the rest of the page.

png format is better for color range and editability however it does create the IE6 problem.

It is a personal choice... I use png where possible.

Soda

Was that only on IEx browsers, or in non-MS browsers too? As mentioned above, IE6 and earlier have had poor PNG support, especially with regards to handling transparency. It's not the PNG format's fault, it's Microsoft's poor support for it. You wouldn't suppose it would have something to do with PNG being an open standard, would you? 

Phil

PNG is a good format to use when you want LOSSLESS image encoding or when you're using palette based images in that the format gives you more options over GIF with better compression (except with GIF you can create animated images which you can't with PNG).  You should however keep in mind that for non palette based images the file size is going to be VERY LARGE compared to using JPEG.  Usually when using PNG files you want to make use of split form image encoding techniques in order retain lossless quality with the smallest file sizes.

For example my blog site:
http://www.backwater-productions.net/hatter-blog/

Is made up of nothing more than this (image wise):
http://www.backwater-productions.net/_images/_Scraps/Split_Form_Blog.png

And actually I could reduce that even further, with the graphic underneath the picture of my face, the entire middle section could be taken out and reduced to a graphic with a width of 1 pixel and then just have it replicated across via code (or use Flash like I did).