Shane is right. You need to set your widths to be percentages. This is rare but if you need to preserve aspect ratio at all times, let me know by @ mentioning me and I’ll hit you with a little trick you can use.
is there a reason why it’s max-width:100% and not width 100%?. Width:100% seems to preserve the aspect ratio too, and there’s no need to assign an auto height.
I usually use
max-width: whatever appropriate value; /* this is used only when I do no want the images to exceed a certain width. For instance, an image within a 250 px wide container(when calculated for the desktop), might become 'huge' when the layout becomes single column, say at 500 or 600 px window width. */