Mobiles and image resizing

I have a site where there is a background image and then several smaller images on a top layer.
The smaller images appear too large on a mobile device. Can anyone tell me the best way to have these smaller images scale on a mobile but leaving the background image untouched?

It’s not a perfect solution, but this CSS code seems to work most of the time:

#mylogo img { max-width:100%; }

Just remember to disable it for your desktop users:

#mylogo img { max-width:none; }

Note that this does not change the amount of data being downloaded–just how the image is displayed in the browser.