One of very few code fragments I haven't touched, because there's nothing to improve, it's perfect (ok, sometimes you may need to store previous document.body.style.overflow - sometimes I force scroll bars on body to avoid layout jumping on reloads with different content lenghts). On Chrome (Linux) it returns zero and it's correct, because it draws the scrollbars somehow different from FF. I think they are outside container box. Anyway - I needed my rendered component to cover all previous container except scroll bars. So I used this method and gues what - it just works. If it doesn't - it's probably a bug in something else. Oh, and I don't even expect it to work in IE <= 8 (but probably it will work in IE7 and 8).

BTW, it should be the part of jQuery and other JS framework. What's the use of $.fn.innerWidth() if it doesn't report REAL inner width?

But meanwhile I am doubt that these values are really useful. I did use it for my combobox script, but I never reached the goal, that I can calculate the real width of scrollbar of the select-field.