- Don't make your visitors download anything to see your site. This includes Flash plugins, Quicktime, and cursors. Especially those dang cursors.
- Don't play music on your site. Midi does awful things to great songs, not to mention the rest of the load time slows when that twangy song is trying to play in the background.
- Backgrounds. Yuck. Don't. Ever. If you wouldn't write a letter on it, don't use it on your website. That simple.
- If you must use blinking and dancing things, limit it to one or even two a page. At three or four, you're pushing it.
- Limit use of graphics - unless you're a graphic site. Too many graphics = slow load time = impatient viewer = stopping the load = going elsewhere
- Broken links. Watch for these - especially the ones you have control over: the ones on your own site.
- And while we're on the subject, make sure font color and background colors are not the same. White font on a white background poses some problems, as you might imagine.
That's my list - for now. There could be other things out there, but I haven't been sufficiently annoyed by anything today to nitpick too much. Must have been some great coffee I had today.