iWeb Optimizer - easily shrink oversized images

Just a couple points:
1. IE/Win still doesn't support alpha-blended transparency in PNG, so in practice you can't really use it on the web for much more than you can GIF--1-bit transparency. Both GIF and PNG are great for lineart-type things, anything with solid colors. The only thing PNG can do that GIF can't is use more than 256 colors, but Photoshop or anything else can optimize which 256 you use so that it looks just fine.

Everything said above about JPEG I agree with. Lossy, anything with text looks like crap.

2. any layout that depends on PNG transparency, I would be pretty worried about it working on IE/Win because of #1.

The PNG v.s. JPG choice depends on the image. Anything with large blocks of colour should be PNG (e.g. the TUAW logo) as it will compress MORE as a PNG and not loose any detail, whereas JPEG will introduce 'noise' around any crisp edges (so the outline of text will look rubbish). For photos, JPEG will produce smaller files and the degradation will be minimal.

PNG : Lossless compression, best for logos, maps, text.
JPEG: Lossy compression, best for photos.

This is no magic bullet. According to reports, the process ruins website designs that depend on transparency. Pretty stupid "fix" don't you think?

I think you can correct this right within the latest version of iWeb. From the help menu...

iWeb: Slow image loading in web browsers

In iWeb 1.0, when you added images to your page they would be converted to PNG format images when published. PNG is a format which allows for image transparency to be displayed in your web browser. However, the downside is that this image format takes up more disk space than a compressed JPEG.

Enhancements in iWeb 1.0.1 allow for most types of images and photo page thumbnails to be published as JPEGs where possible. This translates into faster page loads when people visit your website.

To take advantage of this change in an existing iWeb 1.0 site you'll need to republish all of your pages. To do that, hold down the Option key and from the File menu, choose Publish All to .Mac.

I tried this app. Had a 50mb site before the app and after the app my site forlder was 60.1mb. It had the opposite effect on my website folder. All the files are still PNG.