Interesting. I got some weird behavior for this attribute under Mozilla on Windows (but not on the Mac), but otherwise it seems to work on most of the major browsers.
It's not part of the W3C DOM spec, so you might want to be careful using it if you need broad browser support.
Here's more info.
So, I'll amend my answer to: there's no standards-compliant way to do it that works on all W3C-compliant browsers. But if it works in a subset of browsers that you are interested in, go for it.
hth,
bear