Web images: 7 - two final points
On this page: OK, so I got left with these two points that didn't fit neatly anywhere else! (Left for historical interest.)
Most modern PC graphics cards can support a huge number of display colours - typically 16 million - which is far more than the eye can distinguish, of course. Older cards may only support 256 colours, and ancient ones, just 16.
So, some of your graphics may not look as pretty to everyone as they do to you. If you use GIFs with the so-called web safe palette, then these will usually look similar on all displays, if not aesthetically pleasing. JPEGs generally look better if you use the full palette and let the browser work out how best to display them. I have made a page with three PNG samples at different colour depths - but be warned, the images will take some time to download.
A note on AOL browsers
A frequent complaint by AOL and many CompuServe users used to be that images look fuzzy, blotchy, or have black bars on them. For some reason, AOL chose to add their own extra compression to images - any image viewed in an AOL browser is converted, by default, into a proprietary format called .ART. I have also been told that most images wider than 640 pixels are resized, too. This is enough to make the blood of any graphic designer run cold! But there is not a lot you can do about it - there are probably still a fair few folk out there with these browsers, and the option to turn the feature off is hidden somewhere in the Preferences menu that 99% probably never investigate. AOL itself is rather coy about this: go to webmaster.info.aol.com and use the FAQ link - there is a short article in the graphic section. Also, in the Graphic Info section of the main site, the link to AOL compression says a little bit more.