Read Tim Berners-Lee's style guide for more detail. Add some alternate text to every image, even if it's just the empty string. Click here to see the source code.
Source code is also available.
Some Netscape extensions won't even be displayed under Mosaic or text-only browsers. You can see how your browser treats a set of example tables . Keep all file URLs local. Always provide some warning when an anchor leads to a very large or binary file. The image and source code are available.