found this burried in a recent ajaxian post:

Reserved ID Values?

As a followup to my entry about id=”tags” causing problems in IE/Win, here are four five test pages for IE/Win:

• IE Keyword Testing (length)
• IE Keyword Testing (item)
• IE Keyword Testing (namedItem)
• IE Keyword Testing (tags)
• IE Keyword Testing (urns)

These are based on Kevin Hamilton’s observation that it’s highly likely the problems are caused by the tags method in IE/Win’s document.all DOM interface. As he says:

[I]f you have an element with an id=’tags’, then document.all.tags is now a reference to that element, and no longer a method of the document.all object.

Such states would completely shatter any IE DOM scripting that relied on the document.all methods, and at least in the case of tags causes problems like crashing on print (probably because of the aforementioned conflict between the ID value and the DOM method). The other keywords of concern are chronicled in the test pages listed above. I’d test IE/Win myself, except I don’t have a printer handy for IE/Win to use, and besides, bug-hunting is best conducted in large groups.

Here’s the rest of the article and the test patterns and how to use them.

Thank you Microsoft!
Microsoft’s lame attachEvent protocol (instead of the standard addEventListener) doesn’t pass along the element that caught the event. So if you use attachEvent to attach something to, say, onclick, and then the user clicks that object, then the function you attached can’t do something like “this.id” because “this” isn’t defined. INSTEAD it’s part of the window.event object (there’s only one). this function returns the right object. Call it like so:
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