Web 2.0 style guides

We recieved an email asking:

"I have just started at this software company, and one of my tasks is to work on the writing style guide. I have been looking around on the Internet for a style guide that covers writing style for web applications (or interfaces), and am wondering if you could point me in the right direction. I am looking for a style guide, preferrably in the public domain, that recommends how web-based user interface items should be written in software manuals.

I've looked at a number of company style guides including Microsoft, Sun, and IBM. However, with traditional interface tools like buttons and menu items evolving with the emergence of more sleeker web-based interfaces (rather than the standard dialog boxes that have been around for some time), I was wondering if any software company (or group), besides the ones mentioned, have come up with more up-to-date descriptions of some of these items in their style guide. I would be very happy if you could offer some advice here."

It's a good question. Does anyone know the answer?