How to keyboard down or up between dropdown "options"?

Off the top of my head, I would think that you'd need to maintain some form of a data structure in the JavaScript that reflects the items in the current dropdown list. You'd also need a reference to the currently active/selected item.

Each time keyup or keydown is fired, update the reference to the active/selected item in the data structure. To provide highlighting information on the UI, add or remove a class name that is styled via CSS based on if the item is active/selected or not.

Also, this isn't a biggy, but innerHTML is not really standard (look into createTextNode(), createElement(), and appendChild() for standard ways of creating data). You may also want to see about attaching event handlers in the JavaScript rather than doing so in an HTML attribute.

What you need to do is attach event listeners to the div with id="results". You can do this by adding onkeyup, onkeydown, etc. attributes to the div when you create it or you can attach these using JavaScript.

My recommendation would be that you use an AJAX library like YUI, jQuery, Prototype, etc. for two reasons:

1. It sounds like you are trying to create an Auto Complete control which is something most AJAX libaries should provide. If you can use an existing component you'll save yourself a lot of time.
2. Even if you don't want to use the control provided by a library, all libraries provide event libraries that help to hide the differences between the event APIs provided by different browsers.

Forget addEvent, use Yahoo!’s Event Utility provides a good summary of what an event library should provide for you. I'm pretty sure that the event libraries provided by jQuery, Prototype, et. al. provide similar features.

If that article goes over your head have a look at this documentation first and then re-read the original article (I found the article made much more sense after I'd used the event library).

A couple of other things:

• Using JavaScript gives you much more control than writing onkeyup etc. attributes into your HTML. Unless you want to do something really simple I would use JavaScript.
• If you write your own code to handle keyboard events a good key code reference is really handy.