Now for their comments on Nielsen.
XHTML? Where have you been? Try Googling in ciwah. Internet Explorer is broken. It cannot handle XHTML without some serious hackery. As long as 90% of Web users cannot deal with XHTML qua XHTML, it would be stupid (or ignorant - I've done it myself) to use it.
HTML Strict is the only way to go.
Verdana? ciwas is the place to Google for that. Verdana is produced by Microsoft. In an astonishing act of magnanimity, it is available for Mac as well as Windows. It is not, nor is it ever likely to be, available for Linux, FreeBSD or other systems. That's not a major problem though, is it? After all, CSS provides for graceful degradation by allowing a list of alternative fonts to be suggested. Unfortunately, Verdana lies about its size - at a given nominal size, it is taller and much wider than other faces. That means it is impossible to include Verdana in a list of fonts that will look even vaguely similar.
Flash? There's a saying; well okay, it's not widely known, indeed I coined it myself, but I've been using it in sigs and elsewhere for some time:
Flash doesn't make Web sites inaccessible; trained monkeys make Web sites inaccessible.
Flash isn't necessarily bad. And Macromedia have given serious thought to accessibility issues. But Flash attracts trained monkeys.
The problem with Flash goes deeper than that. I'm willing to entertain the possibility that a competent designer could use Flash to enhance a Web site, but I have never seen an example. Pause a few moments to let that sink in.
I usually use the Web to find information. That usually means reading text. I have never seen a use of Flash that allowed me to find what I was looking for more quickly or easily.
Of course there's more to the Web than text. Occasionally, as with Flickr, images are central to the purpose of a page or an entire site, but a few well-chosen graphics can add life to almost any page. I'm prepared to believe that Flash offers potential benefits that go way beyond simple line graphics or photographic images. but those benefits have a cost. Even with today's broadband links, Flash takes time to download. And I have never seen a Flash movie that was worth waiting for.
And yes, that's a challenge.