I understand now, why I wasn't able to replicate this - 22'' monitor size.
To test you need to shrink browser window for a horizontal scrollbar to appear and then try to scroll right using mouse wheel.
I've searched a bit on the Internet, but was able to found only browser specific code for Gecko & WebKit based browsers, that allow to detect if performed scrolling was horizontal or vertical.
Also I've found that "onmousewheel" javascript event isn't triggered if you have only horizontal and not vertical scrollbar.