deke.com posts about PNG

Deke's Techniques 287: Exporting Your Avatar as a PNG from Photoshop

Deke exports an avatar---born in Photoshop, refined in Illustrator---back to Photoshop for export as a .png file.

Photoshop Top 40, Feature #34: Save for Web (and Devices)

If you're creating Web graphics, there's no substitute for Save for Web. It disposes of non-essential data, reduces file sizes to their absolute minimum, and converts the image to sRGB (the color space of the people).