Size of image before load

We discovered some peculiarities in the way browsers report the size of an image before this image has been loaded by the browser. Here is what we found so far. You may also test it for yourself on our test page, which use this minimal script:

Failed to execute the [code] macro
BrowserwidthoffsetWidthheightoffsetHeight
IE 7/8/9 28 28 30 30
FireFox 3.0/3.5/3.6/4..13 0 0 16 16
FireFox 2.0 / Safari / Chrome / iOS / Android  0 0 0 0