No doubt PNG 32 gives the best resolution
but is it safe to use in all browsers (i.e. is it safe to use in IE6 and up)?

Are there any other reasons not to use PNG32?

I know IE6 has Alpha channel issues with PNG transparency.

But if I am not using transparency is it ok to use PNG32 in IE6?

Anything else I need to know?

if you're not using alpha transparency then it's png 24 anyway

If youre not using transparency, why would you use a png instead of a jpg or gif?
I can only speak for adobe products, but saving any optimized jpg at quality>80 is going to look just about perfect anyhow (at least for web display) and most likely have a smaller filesize than a comparable png file.

Sorry, I realize this doesn't answer your question. I don't really know the answer, but I was just curious as to why you're using png.

if you're not using transparency then there's little to be gained from using a 24-bit png over a jpeg - it will look better, though how noticeable that is compared to a good quality jpeg is negligible, and of course the png will be larger.
there may be some instances where the lossless format of png 24 could be worth considering: one that springs to mind is if you have an image with a mixture of gradients (think jpeg), a colour palette that wouldn't reproduce in 8-bit well, and a lot of solid colour areas as well that would not be suited to jpeg (compression artefacts would be produced) then a 24 bit png could be better suited.

png-8 is better than gif-8 in most cases (i think i read somewhere on a png site that it was 10-15% more efficient than gif.

also if you have adobe fireworks you can get alpha transparency in 8-bit png, though of course it doesn't work in ie6...

incidentally png 24 should be fine in IE6

JPEGs are for photos only.
I suggest you all take a look at this:
http://lbrandy.com/blog/2008/10/my-f...last-webcomic/

PNG (particularly PNG24 or higher) is superior to GIF in that it produces smaller, crisper images.
Particularly so with transparencies.
GIFs are notorious for leaving ugly artifacts behind.
It is also necessary to use PNG format if you want to use a
photographic image on a transparency.

Having said that, PNG alpha channel is not recognized by IE6.
This leaves an ugly, solid color instead of transparency.
The best way I found to overcome this is an excellent JavaScript
patch. You should check this out Drew Diller's "DD_belatedPNG" script.
http://www.dillerdesign.com/experiment/DD_belatedPNG/

PNG files also don't work as repeat background images in IE6, and at
very small pixel sizes, appear problematic in IE7 and even IE8
http://stevelove.org/2009/07/10/png-...lorer-7-and-8/

Information I gathered since my original post.

JPEGs are for photos only.

That's not entirely accurate, they should be used when the image contains a large color pallet. Gifs start to have trouble when fades and gradients are used, for example. You can also lose the gif size advantage if you use a large image that contains a lot of color changes (like text) even if there are a small number of colors.

Gifs should be used when there are larger solid color areas in the image. And depending on the transparency needed, you can get just as clean an edge as a png (at least as far as the eye can tell, which is all that matters) if you used the correct matte color and the background is not too complex.

You are correct that a PNG will usually give you the best quality results, however they will rarely give you the smallest filesize. When working with images that will display in a web browser, filesize should be exactly as important (sometimes more important) than the actual visual quality of the image. It's important to weigh the importance of clarity in your image with the size of the file that will be generated, and the reason why jpgs are used much more often than pngs is because honestly with a png you are not properly balancing these two criteria. If you have a fancy jpg optimizing program (like photoshop) it's a snap to get exactly the balance you want between quality and filesize.

The only time I typically use a png is if I want to get crazy with some overlaping gradients, or use transparencies over complex backgrounds. As for the higher quality, some may prefer png, but I find that I've never met anybody who can tell the visual difference between a png24 and a jpg set at 90+ quality.

Same reason why most people don't care if their mp3 is above 128bit, because 95% of people can't tell the difference anyway.

Oh, and...

PNG (particularly PNG24 or higher) is superior to GIF in that it produces smaller, crisper images.

Sometimes but not always. There are no hard and fast rules about which is better because they all have their own strengths (except bmp, I hate bmp) and the best you can do is learn the strengths of each format so you know when to use what.

Here's a pretty good article that explains exactly what each file format is good at.
http://snook.ca/archives/design/which_image_for/

"Oh, and...
Quote:
PNG (particularly PNG24 or higher) is superior to GIF in that it produces smaller, crisper images.
Sometimes but not always. There are no hard and fast rules about which is better because they all have their own strengths (except bmp, I hate bmp) and the best you can do is learn the strengths of each format so you know when to use what."

well png 24 will always produce better than or at least equal to results than gif because png 24 isn't lossy and doesn't have a palette limited to 256 colours, though of course if you were to compare it on equivalent filesize basis then gif would mostly like win