If you specify width and height explicitly, certain browsers will have issues resizing them (if you set max-width: 100%, Chrome will squish a larger image horizontally but leave the height as it was, IE will scale it proportionally).
I think that's because Chrome treats width= and height= as if they were CSS. (have a look at the inspector on an element with width and height specified in the HTML)
That makes sense (thank you, don't know why I didn't realize that myself), but if I override that with css height: auto; , the browser no longer reserves space for the image while loading it... quite unfortunate.
